import sys
input = sys.stdin.readline

N = int(input())
x = list(map(int, input().split()))
MOD = 10**9+7
S = sum(x)%MOD
T = sum(xi**2%MOD for xi in x)%MOD
ans = (S*S-T)*(S-1)*pow(S*(S-1), MOD-2, MOD)%MOD
ans = (ans+1)%MOD
print(ans)