#include <bits/stdc++.h>
using namespace std;
const int MAXN = 510;
int trap[MAXN], d[MAXN], g[MAXN][MAXN];
double res[MAXN], nxtRes[MAXN];
double mp[MAXN][MAXN * 2], u[120][120], TmpU[120][120];
vector<int> traps;
int main() {
  int n, m, kk, s, t;
  scanf("%d%d%d", &n, &m, &kk);
  for (int i = 0; i < n; i++) {
    scanf("%d", &trap[i]);
    if (trap[i]) traps.push_back(i);
  }
  for (int i = 0; i < m; i++) {
    scanf("%d%d", &s, &t);
    --s, --t;
    ++d[s], ++d[t];
    ++g[s][t], ++g[t][s];
  }
  for (int i = 0; i < n; i++) {
    mp[i][i] = mp[i][i + n] = 1;
    for (int j = 0; j < n; j++)
      if ((!trap[j]) && (j != i)) mp[i][j] = -((double)g[i][j]) / d[j];
  }
  for (int i = 0; i < n; i++) {
    double f = mp[i][i];
    for (int j = 0; j < 2 * n; j++) mp[i][j] /= f;
    for (int j = 0; j < n; j++)
      if (j != i) {
        f = mp[j][i];
        for (int k = 0; k < 2 * n; k++) mp[j][k] -= f * mp[i][k];
      }
  }
  m = traps.size();
  for (int i = 0; i < m; i++) {
    for (int j = 0; j < m; j++) {
      u[j][i] = 0;
      for (int k = 0; k < n; k++)
        u[j][i] += mp[traps[i]][k + n] * g[traps[j]][k] / d[traps[j]];
    }
  }
  kk -= 2;
  for (int i = 0; i < m; i++) res[i] = mp[traps[i]][0 + n];
  for (; kk; kk >>= 1) {
    if (kk & 1) {
      for (int i = 0; i < m; i++) {
        nxtRes[i] = 0;
        for (int j = 0; j < m; j++) {
          nxtRes[i] += res[j] * u[j][i];
        }
      }
      for (int i = 0; i < m; i++) res[i] = nxtRes[i];
    }
    for (int i = 0; i < m; i++)
      for (int j = 0; j < m; j++) {
        TmpU[i][j] = 0;
        for (int k = 0; k < m; k++) {
          TmpU[i][j] += u[i][k] * u[k][j];
        }
      }
    for (int i = 0; i < m; i++)
      for (int j = 0; j < m; j++) {
        u[i][j] = TmpU[i][j];
      }
  }
  printf("%.10lf\n", res[m - 1]);
  return 0;
}
