#include<bits/stdc++.h>
namespace ckain {
//default defines
#define il inline
#define debug(...) fprintf(stderr, __VA_ARGS__)
#define pii pair<int, int>
#define fr first
#define sc second
#define eb emplace_back
#define ll long long
#define mset(f, z) memset(f, z, sizeof(f))
#define mcpy(f, g) memcpy(f, g, sizeof(g))
//default functions
template<typename T=ll>
il T rd() {
	T s=0; bool f=1; char c=getchar();
	while(!isdigit(c)) f^=(c=='-'), c=getchar();
	while(isdigit(c)) s=s*10+c-'0', c=getchar();
	return f? s:-s;
}
template<typename T> il void ckmx(T &x, T y) {if(x<y) x=y;}
template<typename T> il void ckmn(T &x, T y) {if(y<x) x=y;}
}
using namespace std;
using namespace ckain;
char _begin;
#define int ll
const int N=2005, P=1e9+7;

int n, w[N], f[N][N], g[N][N], si[N], sw[N];

void get(int *_g) {
	for(int i=1; i<=n; i++) {
		si[i]=(_g[i]*(i-1)+si[i-1])%P;
		sw[i]=(_g[i]*w[i]+sw[i-1])%P;
	}
}

void solve() {
	for(int i=1; i<=n; i++) {
		w[i]=rd();
		for(int j=1; j<=n; j++) f[i][j]=g[i][j]=0;
	}
	if(n<3) {
		printf("0\n");
		return;
	}
	for(int i=1; i<=n; i++) {
		f[2][i]=i;
		g[2][i]=1;
	}
	for(int i=2; i<n; i++) {
		get(g[i]);
		int sf=0;
		for(int j=1; j<=n; j++) {
			(sf+=f[i][j])%=P;
			(g[i+1][j]+=f[i][j]*w[j])%=P;//p(i+1)<p(i)
			(f[i+1][j]+=sf*w[j])%=P;
			(f[i+1][j]+=si[j]*w[j])%=P;
			(f[i+1][j]+=(sw[n]-sw[j]+P)*j)%=P;
			(g[i+1][j]+=(sw[n]-sw[j]+P))%=P;
			/*
			for(int k=1; k<=n; k++) {
				if(k>=j) (f[i+1][k]+=f[i][j]*w[k])%=P;
				(f[i+1][k]+=g[i][j]*w[max(j, k)]%P*min(j-1, k))%=P;
				if(k<j) (g[i+1][k]+=g[i][j]*w[j])%=P;
			}
			*/
		}
	}
	int ans=0;
	for(int i=1; i<=n; i++) {
		(ans+=f[n][i])%=P;
		(ans+=g[n][i]*(i-1))%=P;
	}
	printf("%lld\n", ans);
}

char _end;
signed main(signed argc, char *argv[]) {
	debug("%lfMB\n", (&_end-&_begin)/1024./1024.);
	while(cin>>n) solve();
	return 0;
}