#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cmath>
#include<iomanip>
#include<cstring>
#include<queue>
#include<ctime>
#include<cstdlib>
using namespace std;
inline int read(){
	int x=0,f=1;char ch=getchar();
	while(ch<'0' || ch>'9')	{if(ch=='-'){f=-1;}ch=getchar();}
	while(ch>='0' && ch<='9')	{x=(x<<1)+(x<<3)+ch-'0';ch=getchar();}
	return x*f;
}
const int mod=1000000007;
int n=0;
int a[100010]={};
int black[100010]={},white[100010]={};
long long ans=0;
void init(){
	n=read();
	for(int i=1;i<=n;i++)
	{
		a[i]=read();
		black[i]=black[i-1];
		white[i]=white[i-1];
		if(a[i]==1)	black[i]++;
		else	white[i]++;
	}
}
void work(){
	for(int i=2;i<n;i++)
	{
		if(a[i]==1)
		{
			int x=white[i-1];
			if(x==0)	continue;
			for(int j=i+1;j<n;j++)
				if(a[j]==2)
				{
					int y=black[n]-black[j];
					ans+=(1LL*x*y)%mod;;
					ans%=mod;
				}
		}
		else
		{
			int x=black[i-1];
			if(x==0)	continue;
			for(int j=i+1;j<n;j++)
				if(a[j]==1)
				{
					int y=white[n]-white[j];
					ans+=(1LL*x*y)%mod;;
					ans%=mod;
				}
		}
	}
}
int main(){
	freopen("asm_code.in","r",stdin);
	freopen("asm_code.out","w",stdout);
	
	init();
	work();
	cout<<ans<<endl;
	
	fclose(stdin);fclose(stdout);
	return 0;
}