#include <bits/stdc++.h>
using namespace std;
vector<vector<double> > mul(const vector<vector<double> > &a,
                            const vector<vector<double> > &b) {
  vector<vector<double> > ret(a.size(), vector<double>(a.size(), 0));
  for (int k = 0; k < a.size(); ++k)
    for (int i = 0; i < a.size(); ++i)
      for (int j = 0; j < a.size(); ++j) ret[i][j] += a[i][k] * b[k][j];
  return ret;
}
vector<int> trap;
int n, m, k;
int ck[505];
int deg[505], edge[505][505];
double mat[505][505 * 2];
int main() {
  scanf("%d%d%d", &n, &m, &k);
  for (int i = 0; i < n; ++i) {
    scanf("%d", ck + i);
    if (ck[i]) trap.push_back(i);
  }
  while (m--) {
    int u, v;
    scanf("%d%d", &u, &v), u--, v--;
    deg[u]++, deg[v]++;
    edge[u][v]++, edge[v][u]++;
  }
  m = trap.size();
  for (int i = 0; i < n; ++i) {
    mat[i][i] = mat[i][n + i] = 1;
    if (!ck[i]) {
      for (int j = 0; j < n; ++j)
        if (i != j) mat[i][j] = -double(edge[i][j]) / deg[i];
    }
  }
  for (int i = 0; i < n; ++i) {
    double h = mat[i][i];
    for (int k = 0; k < 2 * n; ++k) mat[i][k] /= h;
    for (int j = 0; j < n; ++j)
      if (j != i) {
        double t = mat[j][i] / mat[i][i];
        for (int k = 0; k < 2 * n; ++k) mat[j][k] -= t * mat[i][k];
      }
  }
  vector<vector<double> > a(m, vector<double>(m, 0));
  vector<vector<double> > ret(m, vector<double>(m, 0));
  for (int i = 0; i < m; ++i) {
    for (int j = 0; j < m; ++j) {
      int u = trap[i];
      int v = trap[j];
      a[i][j] = 0;
      for (int k = 0; k < n; ++k)
        a[i][j] += mat[k][v + n] * edge[u][k] / deg[u];
    }
  }
  for (int i = 0; i < m; ++i) ret[i][i] = mat[0][trap[i] + n];
  k -= 2;
  while (k) {
    if (k & 1) ret = mul(ret, a);
    a = mul(a, a), k >>= 1;
  }
  double ans = 0;
  for (int i = 0; i < m; ++i) ans += ret[i][m - 1];
  printf("%.5lf\n", ans);
}
