// @Nullptr_qwq @Nullptr_qwQ @Nullptr_qWq @Nullptr_qWQ @Nullptr_Qwq @Nullptr_QwQ @Nullptr_QWq @Nullptr_QWQ
//File uses UTF-8 encoding.
//By: Luogu@tzl_Dedicatus545(UID:308854) Yuanshen@tzl_Dedicatus(UID:273152640)
//Ayaka bless me!
// #define _TZL_DEBUG_
#if defined(_TZL_DEBUG_) && defined(TZL_MEOW)
#define _GLIBCXX_DEBUG
#endif
#include <bits/stdc++.h>
#define int long long
#define ll long long
#define ull unsigned long long
#define rep(i,x,y,z) for(int i=(x),i##misaka=(y);i<=i##misaka;i+=(z))
#define per(i,x,y,z) for(int i=(x),i##mik0t0=(y);i>=i##mik0t0;i-=(z))
#define pb push_back
#define eb emplace_back
#define pii pair<int,int>
#define i128 __int128
#define _1 first
#define _2 second
#define ld long double
#define cint const int
#define pcnt __builtin_popcountll
#define vint vector<int>
#define vpii vector<pair<int,int> >
using namespace std;

const int inf=(sizeof(int)==4?0x3f3f3f3f:0x3f3f3f3f3f3f3f3f);
const int mod=1e9+7;
const long double EPS=1e-7;
const int maxn=2200;
int gcd(int a,int b){
	if(!a || !b)	return a+b;
	unsigned az=__builtin_ctzll(a),bz=__builtin_ctzll(b);unsigned z=min(az,bz);b>>=bz;
	while(a){	a>>=az;int d=a-b;az=__builtin_ctzll(d),b=min(a,b),a=(d<0?-d:d);}
	return b<<z;
}
template<typename T>void chkmin(T& x,const T& y){return y<x?(x=y,void()):void();}
template<typename T>void chkmax(T& x,const T& y){return x<y?(x=y,void()):void();}
bool Mbe;
void inc(int &x,int y){	x=(x+y>=mod?x+y-mod:x+y);}
void dec(int &x,int y){	x=(x-y<0?x-y+mod:x-y);}
int mul(vint vec){int ans=1;for(auto x:vec)	ans*=x,ans%=mod;return ans;}

int fac[maxn],finv[maxn];
ll fpow(ll x,int y){
	ll rt=1;
	for(;y;y>>=1,x=1ll*x*x%mod) if(y&1) rt=1ll*rt*x%mod;
	return rt;
}int inv(int x){	return fpow(x,mod-2);}
void init(int n){
#if 1
	fac[0]=fac[1]=1;finv[0]=finv[1]=1;
	rep(i,2,n,1){	fac[i]=1ll*fac[i-1]*i%mod;}finv[n]=inv(fac[n]);
	per(i,n-1,1,1){	finv[i]=1ll*finv[i+1]*(i+1)%mod;}
#endif
}int C(int n,int m){
	if(n<m || n<0 || m<0)	return 0;
	return 1ll*fac[n]*finv[m]%mod*finv[n-m]%mod;
}

int w[maxn];
int f[maxn][maxn][3];
int sa[maxn];

bool Med;
signed main()
{ios::sync_with_stdio(0);cin.tie(0);init(maxn-1);cerr<<fixed<<setprecision(3)<<(&Mbe-&Med)/1048576.0<<"MiB"<<endl;
	int n;
	while(cin>>n){
		rep(i,1,n,1)	cin>>w[i];
		rep(i,0,n,1)	rep(j,0,n,1)	rep(k,0,2,1)	f[i][j][k]=0;
		rep(v,1,n,1)	f[1][v][0]=w[v],f[1][v][1]=w[v]*(v-1)%mod,f[1][v][2]=w[v]*(v-1)*(v-1)%mod;
		rep(i,1,n-2,1){
			int pr=0;
			rep(v,0,n+1,1)	sa[v]=0;
			per(v,n,1,1)	sa[v]=sa[v+1]+f[i-1][v][0]; 
			rep(v,1,n,1){
				
				if(i!=1){
					inc(f[i][v][2],pr);
					inc(f[i][v][0],sa[v]);
					inc(f[i][v][1],sa[v]*(v-1)%mod);
					inc(f[i][v][2],sa[v]*(v-1)*(v-1)%mod);
					rep(j,0,2,1)	f[i][v][j]*=w[v],f[i][v][j]%=mod;
				}
				
				inc(f[i+1][v][0],f[i][v][1]);inc(f[i+1][v][1],f[i][v][2]);
				/*
				rep(vt,1,n,1){
					if(vt<=v){
						inc(f[i+1][vt][0],f[i][v][0]%mod);	
						inc(f[i+1][vt][1],f[i][v][0]*(vt-1)%mod);
					}	
					
					if(vt<=v)	inc(f[i+1][vt][2],f[i][v][0]*(vt-1)*(vt-1));
				}
				*/
				pr+=(f[i-1][v][1]*v+f[i-1][v][2])%mod+f[i-1][v][0]*v*v%mod;pr%=mod;
			}
		}
		int ans=0;	
		rep(v,1,n,1)	inc(ans,f[n-2][v][0]*(v)%mod*(v)%mod),inc(ans,f[n-2][v][1]*(v)%mod),inc(ans,f[n-2][v][2]);
		cout<<ans<<endl;
	}
	return 0;
}