#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cmath>
#include<queue>
#include<vector>
#include<cstring>
#include<string>
#include<cstdlib>
#include<set>
#include<map>
using namespace std;
int n;
int curh,curb,zuo1=0,zuo2=0;
int a[2010];
int hi=0,bi=0;
long long ans=0;
int fun(int cur,int x,int y){
	ans=(ans+(bi-x)*x*y)%1000000007;
	
}
int main(){
	freopen("asm_code.in","r",stdin);
	freopen("asm_code.out","w",stdout);
	cin>>n;
	for(int i=1;i<=n;i++){
		cin>>a[i];
		if(a[i]==1) hi++;
		else bi++;
		
	}
	for(int i=1;i<=n;i++)
	{
		if(a[i]==1)
		{
		 fun(i,zuo1,zuo2);
		 zuo2++;
	    }
		else zuo1++;
	}
	cout<<ans%1000000007;
	return 0;
	
}