func_code_string: #include <bits/stdc++.h>   using std::cin;   using std::cout;   const int N = 5054, mod = 1000000007;   int n, K;   int f[N];   long long PowerMod(long long a, int n, long long c = 1) {     for (; n; n >>= 1, a = a * a % mod)       if (n & 1) c = c * a % mod;     return c;   }   int main() {     int i, j, x, in, ans = 0;     std::ios::sync_with_stdio(false), cin.tie(NULL);     cin >> n >> K, *f = 1, in = PowerMod(n, mod - 2);     for (i = 0; i < n; ++i) {       cin >> x;       for (j = i + 1; j; --j) f[j] = ((long long)f[j] * x + mod - f[j - 1]) % mod;       *f = (long long)*f * x % mod;     }     for (x = mod - 1, i = 1; i <= n && i <= K; ++i)       x = x * (K - i + 1ll) % mod * in % mod,       ans = (ans + (long long)x * f[i]) % mod;     cout << ans <<   n ;     return 0;   }   