#include <cstdio> #include <iostream> #include <algorithm> #include <cstring> using namespace std; int n, m, a[30]; long long cnt[60][60]; int main() { cin >> n; for (int i = 1; i <= n; i++) { cin >> a[i]; m += a[i]; } for (int i = 0; i <= 50; i++) cnt[i][0] = cnt[i][i] = 1; for (int i = 0; i <= 50; i++) for (int j = 1; j < i; j++) cnt[i][j] = cnt[i - 1][j] + cnt[i - 1][j - 1]; long long ans = 1; for (int i = 2; i <= n; i++) { ans *= cnt[m - 1][m - a[i - 1]]; m -= a[i - 1]; } cout << ans << endl; return 0; }