#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#include <map>
#include <vector>
#include <queue>
#include <deque>
#include <set>
#include <stack>
#include <algorithm>
#include <array>
#include <unordered_set>
#include <unordered_map>
#include <string>
using namespace std;

bool rcmp(int a, int b) { return a>b; }
typedef long long LL;


#define MOD 1000000007
int xs[100004];

int expit(LL b, LL e) {
    LL r=1;
    while(e) {
        if (e&1) { r*=b; r%=MOD; }
        b*=b; b%=MOD; 
        e>>=1;
    }
    return r;
}
int main() {
    int n, i;
    LL s=0, r=0, t1, t2, t, c;
    scanf("%d", &n);
    for (i=0; i<n; i++) {
        scanf("%d", &xs[i]);
        s+=xs[i];
    }
    for (i=0; i<n; i++) {
        c=xs[i];
        r+=1; r%=MOD;
        //
        // t = 1-(1-1/(c+1))**(s-c)
        t1 = c;// expit(c, s-c);
        // t2 = expit(c+1, s-c);
        t2 = expit(s, MOD-2);
        t1*=t2; t1%=MOD;
        t  = 1-t1; if (t<0) t+=MOD;
        t*=(c-1); t%=MOD;
        r+=t; r%=MOD;
    }
    printf("%lld\n", r);
    return 0;
}