zx

import java.util.Arrays;

public class Permutant {
  public int mod = 1000000007;
  public int counthis(int[] a) {
    int n = a.length;
    int m = 0;
    for (int x : a) m += x;
    long[][] comb = new long[m+1][m+1];
    comb[0][0] = 1;
    for (int i = 1; i <= m; i++) {
      comb[i][0] = 1;
      for (int j = 1; j <= i; j++) {
        comb[i][j] = (comb[i-1][j] + comb[i-1][j-1]) % mod;
      }
    }
    long[] fact = new long[m+1];
    fact[0] = 1;
    for (int i = 1; i <= m; i++) {
      fact[i] = fact[i-1] * i % mod;
    }

    long ret = 0;
    for (int last = 0; last < n; last++) {
      // dp[i] = number of ways given there are i balls to the right of the first occurrence of a ball of the last color.
      long[] dp = new long[m+1];
      // can freely arrange all the balls of the last color
      dp[a[last] - 1] = fact[a[last]];
      int cursum = a[last]-1;
      for (int i = 0; i < n; i++) {
        if (last == i) continue;
        long[] next = new long[m+1];
        // need to put at least one ball to the left
        for (int left = 1; left <= a[i]; left++) {
          int right = a[i] - left;
          for (int curright = 0; curright <= cursum && curright+right <= m; curright++) {
            int curleft = cursum - curright;
            // since the first occurrence of each color needs to be label 1, this is fact[a[i]-1] instead of fact[a[i]].
            long y = fact[a[i]-1] * comb[curleft+left][left] % mod * comb[curright+right][right] % mod;
            next[curright+right] = (next[curright+right] + dp[curright] * y) % mod;
          }
        }
        dp = next;
        cursum += a[i];
      }
      for (int i = 0; i <= m; i++)
        ret = (ret + dp[i]) % mod;
    }
    return (int)ret;
  }
}