#include <bits/stdc++.h>
using namespace std;
char string_in_buffer[(int)260];
void fast_scan(int &first) { scanf("%d", &first); }
void fast_scan(long long &first) { scanf("%lld", &first); }
void fast_scan(unsigned long long &first) { scanf("%llu", &first); }
void fast_scan(double &first) { scanf("%lf", &first); }
void fast_scan(long double &first) { scanf("%Lf", &first); }
void fast_scan(char &first) {
  scanf("%c", &first);
  if (first == '\n') {
    fast_scan(first);
  }
}
void fast_scan(string &first) {
  scanf("%s", string_in_buffer);
  first = string(string_in_buffer);
}
template <class TFirst, class TSecond>
void fast_scan(pair<TFirst, TSecond> &p) {
  fast_scan(p.first);
  fast_scan(p.second);
}
template <class T>
void fast_scan(vector<T> &v) {
  for (auto &first : v) fast_scan(first);
}
void fast_print(const int &first) { printf("%d", first); }
void fast_print(const unsigned int &first) { printf("%u", first); }
void fast_print(const long long &first) { printf("%lld", first); }
void fast_print(const unsigned long long &first) { printf("%llu", first); }
void fast_print(const double &first) { printf("%.15lf", first); }
void fast_print(const float &first) { printf("%.15f", first); }
void fast_print(const long double &first) { printf("%.15Lf", first); }
void fast_print(const char &first) { printf("%c", first); };
void fast_print(const string &first) { printf("%s", first.c_str()); }
void fast_print(const char v[]) { fast_print((string)v); }
template <class TFirst, class TSecond>
void fast_print(const pair<TFirst, TSecond> &p) {
  fast_print(p.first);
  fast_print(' ');
  fast_print(p.second);
}
template <class T>
void fast_print(const vector<T> &v) {
  if (v.empty()) return;
  fast_print(v[0]);
  for (int i = 1; i < v.size(); i++) {
    fast_print(' ');
    fast_print(v[i]);
  }
}
template <class T>
void fast_print(const vector<vector<T>> &v) {
  if (v.empty()) return;
  fast_print(v[0]);
  for (int i = 1; i < v.size(); i++) {
    fast_print('\n');
    fast_print(v[i]);
  }
}
template <class T>
void fast_print(const T &v) {
  for (const auto &first : v) {
    fast_print(first);
    fast_print(' ');
  }
}
using namespace std;
namespace smart_io {
string print_start = "";
string sep = " ";
bool first_print = false;
void precall_print() {
  fast_print(print_start);
  print_start = "\n";
  first_print = true;
}
void _print(deque<string>) {}
template <class T, class... Args>
void _print(deque<string> names, T elem, Args... args) {
  if (!first_print) {
    fast_print("\n");
  } else {
    first_print = false;
  }
  fast_print(names.front());
  fast_print(" = ");
  fast_print(elem);
  names.pop_front();
  _print(names, args...);
}
}  // namespace smart_io
template <class T>
ostream &operator,(ostream &os, const T &object) {
  if (!smart_io::first_print) {
    fast_print(smart_io::sep);
  } else {
    smart_io::first_print = false;
  }
  fast_print(object);
  return os;
}
template <class T>
istream &operator,(istream &is, T &object) {
  fast_scan(object);
  return is;
}
namespace typedefs {}
namespace numbers_operation {
template <class T>
T floor_mod(T a, T b) {
  if (a % b == 0) return 0;
  if (a >= 0 && b >= 0) return a % b;
  if (a <= 0 && b <= 0) return a % b;
  return abs(b) - (abs(a) % abs(b));
}
}  // namespace numbers_operation
using namespace numbers_operation;
using namespace typedefs;
int n, m, k;
vector<vector<int>> g;
vector<int> trap;
vector<int> ztraps;
int traps = 0;
vector<vector<double>> gauss(vector<vector<double>> M) {
  for (int i = 0; i < (((int)M[0].size())); i++) {
    int unz = 0;
    for (int j = 0; j < (((int)M.size())); j++) {
      if (abs(M[j][i]) > abs(M[unz][i])) {
        unz = j;
      }
    }
    if (M[unz][i] == 0) continue;
    double cor = M[unz][i];
    for (int j = 0; j < (((int)M[0].size())); j++) {
      M[unz][j] /= cor;
    }
    for (int j = 0; j < (((int)M.size())); j++) {
      double coef = M[j][i] / M[unz][i];
      for (int k = 0; k < (((int)M[0].size())); k++) {
        M[j][k] -= coef * M[unz][k];
      }
    }
  }
  return M;
}
vector<vector<double>> merge(vector<vector<double>> A,
                             vector<vector<double>> B) {
  vector<vector<double>> C(traps, vector<double>(traps));
  for (int st = 0; st < (traps); st++) {
    for (int inter = 0; inter < (traps); inter++) {
      for (int end = 0; end < (traps); end++) {
        C[st][end] += A[st][inter] * B[inter][end];
      }
    }
  }
  return C;
}
vector<double> operator*(vector<double> v, double d) {
  for (double &first : v) {
    first *= d;
  }
  return v;
}
vector<double> operator+(vector<double> a, vector<double> b) {
  assert(((int)a.size()) == ((int)b.size()));
  for (int i = 0; i < (((int)b.size())); i++) {
    a[i] += b[i];
  }
  return a;
}
vector<double> operator-(vector<double> a, vector<double> b) {
  return a + (b * -1);
}
vector<vector<double>> get_first() {
  vector<vector<double>> prob(n, vector<double>(n));
  for (int i = 0; i < n; i++) {
    if (trap[i]) {
      prob[i][i] = 1;
    } else {
      for (int j : g[i]) {
        prob[i][j] += 1.0 / ((int)g[i].size());
      }
    }
  }
  vector<vector<double>> R(n, vector<double>(n));
  for (int i = 0; i < n; i++) {
    prob[i][i] -= 1;
  }
  for (int i = 0; i < n; i++) {
    for (int j = 0; j < n; j++) {
      if (trap[j]) {
        R[i][j] = -prob[i][j];
        prob[i][j] = 0;
      }
    }
  }
  for (int i = 0; i < n; i++) {
    if (trap[i]) continue;
    for (int j = i + 1; j < n; j++) {
      if (abs(prob[j][i]) > abs(prob[i][i])) {
        swap(prob[j], prob[i]);
        swap(R[j], R[i]);
      }
    }
    for (int j = i + 1; j < n; j++) {
      double cor = prob[j][i] / prob[i][i];
      for (int k = 0; k < n; k++) {
        prob[j][k] -= cor * prob[i][k];
        R[j][k] -= cor * R[i][k];
      }
    }
  }
  vector<vector<double>> final(n, vector<double>(n));
  for (int i = n - 1; i > -1; i--) {
    if (trap[i]) continue;
    for (int j = 0; j < n; j++) {
      R[i][j] /= prob[i][i];
    }
    prob[i][i] = 1;
    for (int j = 0; j < i; j++) {
      for (int k = 0; k < n; k++) {
        R[j][k] -= prob[j][i] * R[i][k];
      }
      prob[j][i] = 0;
    }
  }
  vector<vector<double>> next(n, vector<double>(n));
  for (int i = 0; i < n; i++) {
    if (trap[i]) {
      R[i] = vector<double>(n, 0);
      R[i][i] = 1;
    }
    double c = 1;
    for (int j = 0; j < n; j++) {
      c -= R[i][j];
    }
  }
  return R;
}
vector<vector<double>> one;
vector<vector<double>> fast_pow(int k) {
  if (k == 1) {
    if (!one.empty()) return one;
    vector<vector<double>> F = get_first();
    vector<vector<double>> P(traps, vector<double>(traps));
    for (int i = 0; i < (traps); i++) {
      for (int j = 0; j < (traps); j++) {
        for (int sub : g[ztraps[i]]) {
          P[i][j] += F[sub][ztraps[j]];
        }
        P[i][j] /= ((int)g[ztraps[i]].size());
      }
    }
    return one = P;
  } else {
    if (k % 2 == 0) {
      vector<vector<double>> first = fast_pow(k / 2);
      return merge(first, first);
    } else {
      vector<vector<double>> first = fast_pow(k - 1);
      return merge(first, fast_pow(1));
    }
  }
}
signed main(signed argc, char *argv[]) {
  cin, n, m, k;
  trap.resize(n);
  g.resize(n);
  cin, trap;
  for (int i = 0; i < (n); i++) {
    traps += trap[i];
    if (trap[i]) {
      ztraps.push_back(i);
    }
  }
  for (int i = 0; i < (m); i++) {
    int a, b;
    cin, a, b;
    a--;
    b--;
    g[a].push_back(b);
    g[b].push_back(a);
  }
  if (k == 2) {
    vector<vector<double>> F = get_first();
    smart_io::precall_print();
    cout, F[0][n - 1];
  } else {
    vector<vector<double>> P = fast_pow(k - 2);
    vector<vector<double>> F = get_first();
    double rez = 0;
    for (int i = 0; i < (traps); i++) {
      rez += F[0][ztraps[i]] * P[i][traps - 1];
    }
    smart_io::precall_print();
    cout, rez;
  }
}
