#include <cstdlib>
#include <iostream>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <map>
#include <stack>
#include <vector>
#include <map>
#include <queue>
#include <ctime>
#include <algorithm>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
typedef unsigned int uint;
const int inf=1061109567;
const int maxn=100010;
const int maxm=110;
const int mod=1000000007;
const double pi=3.14;
 
int a[maxn];
int f[maxn];
int g[maxn];
int fnt[maxn];
int lst[maxn];
 
int main()
{
    freopen("asm_code.in","r",stdin);
    freopen("asm_code.out","w",stdout);
    //clock_t st=clock();
    int n;scanf("%d",&n);
    for(int i=1;i<=n;i++)
    {
        scanf("%d",&a[i]);
        f[i]=f[i-1];g[i]=g[i-1];
        if(a[i]==1) f[i]++;
        else g[i]++;
    }
    for(int i=1;i<=n;i++)
    {
        if(a[i]==1) fnt[i]=g[i],lst[i]=g[n]-g[i];
        else fnt[i]=f[i],lst[i]=f[n]-f[i];
    }
    ll ans=0,tmp;int cnt;
    for(int i=1;i<=n;i++)
    {
        if(a[i]==2) continue;
        cnt=0;
        for(int j=i+1;j<=n;j++)
        {
            if(a[j]==2) cnt++;
            else
            {
                tmp=(cnt*((fnt[i]+lst[j])%mod))%mod;
                ans=(ans+tmp)%mod;
            }
        }
    }
    printf("%lld\n",ans);
    //clock_t ed=clock();
    //printf("\nTime used : %.5lf Ms\n",double(ed-st)/CLOCKS_PER_SEC);
    return 0;
}