#include <bits/stdc++.h>
using namespace std;
template <typename T, typename U>
std::istream &operator>>(std::istream &i, pair<T, U> &p) {
  i >> p.first >> p.second;
  return i;
}
template <typename T>
std::istream &operator>>(std::istream &i, vector<T> &t) {
  for (auto &v : t) {
    i >> v;
  }
  return i;
}
template <typename T, typename U>
std::ostream &operator<<(std::ostream &o, const pair<T, U> &p) {
  o << p.first << ' ' << p.second;
  return o;
}
template <typename T>
std::ostream &operator<<(std::ostream &o, const vector<T> &t) {
  if (t.empty()) o << '\n';
  for (size_t i = 0; i < t.size(); ++i) {
    o << t[i] << " \n"[i == t.size() - 1];
  }
  return o;
}
template <typename T>
using minheap = priority_queue<T, vector<T>, greater<T>>;
template <typename T>
using maxheap = priority_queue<T, vector<T>, less<T>>;
template <typename T>
bool in(T a, T b, T c) {
  return a <= b && b < c;
}
unsigned int logceil(int first) {
  return 8 * sizeof(int) - __builtin_clz(first);
}
namespace std {
template <typename T, typename U>
struct hash<pair<T, U>> {
  hash<T> t;
  hash<U> u;
  size_t operator()(const pair<T, U> &p) const {
    return t(p.first) ^ (u(p.second) << 7);
  }
};
}  // namespace std
template <typename T, typename F>
T bsh(T l, T h, const F &f) {
  T r = -1, m;
  while (l <= h) {
    m = (l + h) / 2;
    if (f(m)) {
      l = m + 1;
      r = m;
    } else {
      h = m - 1;
    }
  }
  return r;
}
template <typename F>
double bshd(double l, double h, const F &f, double p = 1e-9) {
  unsigned int r = 3 + (unsigned int)log2((h - l) / p);
  while (r--) {
    double m = (l + h) / 2;
    if (f(m)) {
      l = m;
    } else {
      h = m;
    }
  }
  return (l + h) / 2;
}
template <typename T, typename F>
T bsl(T l, T h, const F &f) {
  T r = -1, m;
  while (l <= h) {
    m = (l + h) / 2;
    if (f(m)) {
      h = m - 1;
      r = m;
    } else {
      l = m + 1;
    }
  }
  return r;
}
template <typename F>
double bsld(double l, double h, const F &f, double p = 1e-9) {
  unsigned int r = 3 + (unsigned int)log2((h - l) / p);
  while (r--) {
    double m = (l + h) / 2;
    if (f(m)) {
      h = m;
    } else {
      l = m;
    }
  }
  return (l + h) / 2;
}
template <typename T>
T gcd(T a, T b) {
  if (a < b) swap(a, b);
  return b ? gcd(b, a % b) : a;
}
template <typename T>
class vector2 : public vector<vector<T>> {
 public:
  vector2() {}
  vector2(size_t a, size_t b, T t = T())
      : vector<vector<T>>(a, vector<T>(b, t)) {}
};
template <typename T>
class vector3 : public vector<vector2<T>> {
 public:
  vector3() {}
  vector3(size_t a, size_t b, size_t c, T t = T())
      : vector<vector2<T>>(a, vector2<T>(b, c, t)) {}
};
template <typename T>
class vector4 : public vector<vector3<T>> {
 public:
  vector4() {}
  vector4(size_t a, size_t b, size_t c, size_t d, T t = T())
      : vector<vector3<T>>(a, vector3<T>(b, c, d, t)) {}
};
template <typename T>
class vector5 : public vector<vector4<T>> {
 public:
  vector5() {}
  vector5(size_t a, size_t b, size_t c, size_t d, size_t e, T t = T())
      : vector<vector4<T>>(a, vector4<T>(b, c, d, e, t)) {}
};
template <typename T>
class Matrix {
 public:
  Matrix(size_t R, size_t C, T t = T(0))
      : R(R), C(C), A(R, vector<T>(C, t)), def(t) {}
  Matrix(const vector<vector<T>> &a, T t = T(0))
      : R(a.size()), C(a[0].size()), A(a), def(t) {}
  Matrix(const initializer_list<vector<T>> &a, T t = T(0))
      : R(a.size()), C(a.begin()->size()), A(a), def(t) {}
  size_t rows() const { return R; }
  size_t columns() const { return C; }
  bool isSquare() const { return R * C; }
  bool isIdentity() const {
    for (int i = 0; i < min(R, C); ++i) {
      for (int j = 0; j < min(R, C); ++j) {
        if (i == j && A[i][j] != 1) return false;
        if (i != j && A[i][j] != 0) return false;
      }
    }
    return true;
  }
  void addColumnsRight(size_t add, T t = T()) {
    for (int i = 0; i < R; ++i) {
      A[i].resize(C + add);
      for (size_t j = C; j < C + add; ++j) A[i][j] = t;
    }
    C += add;
  }
  void removeColumnsLeft(size_t rem) {
    for (size_t i = 0; i < R; ++i)
      A[i].erase(A[i].begin(),
                 rem > A[i].size() ? A[i].end() : A[i].begin() + rem);
  }
  T determinant() const {
    if (!isSquare()) {
      throw std::runtime_error(
          "Cannot compute determinant of a rectangular matrix");
    }
    Matrix<T> tmp(*this);
    T ans = tmp.toReducedRowEchelon();
    if (tmp.isIdentity())
      return ans;
    else
      return 0;
  }
  vector<T> solveFor(const vector<T> &b) {
    if (!isSquare()) {
      throw std::runtime_error("Cannot solve a rectangular matrix");
    }
    if (b.size() != R)
      throw new std::runtime_error(
          "Unable to solve linear equation, dimensions do not match");
    Matrix<T> tmp(*this);
    for (int i = 0; i < R; ++i) tmp.A[i].push_back(b[i]);
    ++tmp.C;
    tmp.toReducedRowEchelon();
    if (!tmp.isIdentity())
      throw std::runtime_error("Cannot solve a singular matrix");
    vector<T> Ans(R);
    for (int j = 0; j < R; ++j) Ans[j] = tmp.A[j].back();
    return Ans;
  }
  Matrix<T> power(unsigned long long N) {
    if (!isSquare()) {
      throw std::runtime_error(
          "Cannot compute determinant of a rectangular matrix");
    }
    Matrix<T> ans(R, R, 0), pow = *this;
    for (unsigned int r = 0; r < R; ++r) ans[r][r] = 1;
    while (N) {
      if (N & 1) ans = ans * pow;
      N >>= 1;
      pow = pow * pow;
    }
    return ans;
  }
  Matrix<T> &operator+=(const Matrix<T> &m) {
    if (R != m.R)
      throw std::runtime_error("Cannot add matrices of different height");
    if (C != m.C)
      throw std::runtime_error("Cannot add matrices of different width");
    for (int i = 0; i < R; ++i) {
      for (int j = 0; j < C; ++j) {
        A[i][j] += m.A[i][j];
      }
    }
    return *this;
  }
  Matrix<T> &operator-=(const Matrix<T> &m) {
    if (R != m.R)
      throw std::runtime_error("Cannot substract matrices of different height");
    if (C != m.C)
      throw std::runtime_error("Cannot substract matrices of different width");
    for (int i = 0; i < R; ++i) {
      for (int j = 0; j < C; ++j) {
        A[i][j] -= m.A[i][j];
      }
    }
    return *this;
  }
  Matrix<T> operator*(const Matrix<T> &m) const {
    if (C != m.R)
      throw std::runtime_error("Matrices incompatible for multiplication");
    Matrix<T> Ans(R, m.C, T(0));
    for (int i = 0; i < R; ++i) {
      for (int j = 0; j < m.C; ++j) {
        for (int k = 0; k < C; ++k) {
          Ans[i][j] += A[i][k] * m.A[k][j];
        }
      }
    }
    return Ans;
  }
  vector<T> operator*(const vector<T> &m) const {
    if (C != m.size())
      throw std::runtime_error(
          "Matric and vector incompatible for multiplication");
    vector<T> ans(R, def);
    for (unsigned int r = 0; r < R; ++r) {
      for (unsigned int c = 0; c < C; ++c) {
        ans[r] += m[c] * (*this)[r][c];
      }
    }
    return ans;
  }
  class Row {
   public:
    Row(Matrix<T> *M, size_t row) : M(M), row(row) {}
    T &operator[](size_t col) {
      if (col < 0 || col >= M->C) throw std::out_of_range("Invalid column ID");
      return M->A[row][col];
    }
    const T &operator[](size_t col) const {
      if (col < 0 || col >= M->C) throw std::out_of_range("Invalid column ID");
      return M->A[row][col];
    }

   private:
    Matrix<T> *M;
    size_t row;
  };
  Row operator[](size_t row) {
    if (row < 0 || row >= R) throw std::out_of_range("Invalid row ID");
    return Row(this, row);
  }
  const Row operator[](size_t row) const {
    if (row < 0 || row >= R) throw std::out_of_range("Invalid row ID");
    return Row(const_cast<Matrix<T> *>(this), row);
  }
  Matrix<T> transposed() const {
    Matrix<T> M(*this);
    M.transpose();
    return M;
  }
  Matrix<T> inverted() const {
    if (R != C) throw std::runtime_error("Matrix not square");
    Matrix<T> M(*this);
    M.invert();
    return M;
  }
  Matrix<T> &transpose() {
    A.resize(max(R, C));
    for (size_t i = 0; i < C; ++i) A[i].resize(max(R, C));
    for (size_t i = 0; i < R; ++i) {
      for (size_t j = i + 1; j < C; ++j) swap(A[i][j], A[j][i]);
    }
    for (size_t i = 0; i < C; ++i) A[i].resize(R);
    A.resize(C);
    return *this;
  }
  Matrix<T> &invert() {
    addColumnsRight(C, def);
    for (size_t i = 0; i < R; ++i) A[i][R + i] = 1;
    toReducedRowEchelon();
    if (!isIdentity()) throw std::runtime_error("Matrix not invertible");
    removeColumnsLeft(C / 2);
    return *this;
  }

 private:
  T toReducedRowEchelon() {
    size_t pivot = 0;
    T factor = 1;
    for (size_t i = 0; i < C && pivot < R; ++i) {
      pair<T, size_t> Q = {A[pivot][i], pivot};
      for (size_t j = pivot + 1; j < R; ++j)
        if (A[j][i] != 0) Q = {A[j][i], j};
      if (Q.first == 0) continue;
      if (Q.second != i) swap(A[Q.second], A[pivot]);
      for (size_t j = i + 1; j < C; ++j) A[pivot][j] /= A[pivot][i];
      factor /= A[pivot][i];
      A[pivot][i] = 1;
      for (size_t j = 0; j < R; ++j) {
        if (j != pivot) {
          for (size_t k = i + 1; k < C; ++k) A[j][k] -= A[pivot][k] * A[j][i];
          A[j][i] = 0;
        }
      }
      ++pivot;
    }
    return factor;
  }
  size_t R, C;
  vector<vector<T>> A;
  T def;
};
template <typename T>
std::ostream &operator<<(std::ostream &os, const Matrix<T> &m) {
  for (size_t r = 0; r < m.rows(); ++r)
    for (size_t c = 0; c < m.columns(); ++c)
      os << m[r][c] << " \n"[c == m.columns() - 1];
  return os;
}
class TaskD {
 public:
  void solve(istream &cin, ostream &cout) {
    int N, M, K;
    cin >> N >> M >> K;
    vector<vector<int>> E(N);
    vector<int> T(N);
    cin >> T;
    for (int i = 0; i < M; ++i) {
      int u, v;
      cin >> u >> v;
      --u;
      --v;
      E[u].push_back(v);
      E[v].push_back(u);
    }
    vector2<double> D(N, N, 0);
    for (int u = 0; u < N; ++u) {
      for (int v : E[u]) {
        D[u][v] += 1.0 / E[u].size();
      }
    }
    auto relax = [&](int v) {
      if (D[v][v] > 1e-10) {
        for (int w = 0; w < N; ++w) {
          if (v != w) {
            D[v][w] /= (1 - D[v][v]);
          }
        }
        D[v][v] = 0;
      }
      for (int u = 0; u < N; ++u) {
        if (u != v && D[u][v] > 1e-10) {
          for (int w = 0; w < N; ++w) {
            if (w != v && D[v][w] > 1e-10) {
              D[u][w] += D[u][v] * D[v][w];
            }
          }
        }
      }
      for (int u = 0; u < N; ++u) {
        D[u][v] = 0;
        D[v][u] = 0;
      }
    };
    for (int v = 0; v < N; ++v) {
      if (v != 0 && !T[v]) {
        relax(v);
      }
    }
    vector<double> Init;
    for (int u = 0; u < N; ++u) {
      if (T[u]) {
        Init.push_back(D[0][u] / (1 - D[0][0]));
      }
    }
    vector<vector<double>> Trans;
    relax(0);
    for (int u = 0; u < N; ++u) {
      if (T[u]) {
        Trans.push_back({});
        for (int v = 0; v < N; ++v) {
          if (T[v]) {
            Trans.back().push_back(D[u][v]);
          }
        }
      }
    }
    Matrix<double> A(Trans);
    auto L = A.power(K - 2).transpose() * Init;
    cout << fixed << setprecision(10) << L.back() << endl;
  }
};
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  cout.tie(nullptr);
  TaskD solver;
  std::istream &in(std::cin);
  std::ostream &out(std::cout);
  solver.solve(in, out);
  return 0;
}
