#include <bits/stdc++.h>
using namespace std;
const int mo = 1000000007;
typedef long long int i64;
const int maxn = 100333;
int n, S[maxn], A[maxn], dd[maxn];
int main()
{
    freopen("asm_code.in", "r", stdin);
#ifndef debug
    freopen("asm_code.out", "w", stdout);
#endif
    scanf("%d", &n); int cnt = 0; 
    for (int i = 1; i <= n; ++i)
    {
        int ty; scanf("%d", &ty);
        if (ty == 2) ++S[i];
        else dd[cnt++] = i;
    }
    for (int i = 1; i <= n; ++i) S[i] += S[i - 1];
    for (int i = 0; i < cnt; ++i) A[i] = S[dd[i]];
    int  M = S[n], ans2 = 0, l1 = 0, l2 = 0;;
    for (int i = cnt - 1; i >= 0; --i)
    {
        (ans2 += (i64(cnt - i - 1) * (mo - M - A[i]) % mo * A[i] % mo + l1 + 2LL * A[i] * l2) % mo) %= mo;
        (l1 += i64(M - A[i]) * A[i] % mo ) %= mo;
        (l2 += A[i]) %= mo;
    }

    printf("%d\n", ans2);

}