#include <bits/stdc++.h>
using namespace std;
inline long long read() {
  char c = getchar();
  long long x = 0;
  bool f = 0;
  for (; !isdigit(c); c = getchar()) f ^= !(c ^ 45);
  for (; isdigit(c); c = getchar()) x = (x << 1) + (x << 3) + (c ^ 48);
  if (f) x = -x;
  return x;
}
struct modint {
  long long x;
  modint(long long o = 0) { x = o; }
  modint &operator=(long long o) { return x = o, *this; }
  modint &operator+=(modint o) {
    return x = x + o.x >= 1000000007 ? x + o.x - 1000000007 : x + o.x, *this;
  }
  modint &operator-=(modint o) {
    return x = x - o.x < 0 ? x - o.x + 1000000007 : x - o.x, *this;
  }
  modint &operator*=(modint o) { return x = 1ll * x * o.x % 1000000007, *this; }
  modint &operator^=(long long b) {
    modint a = *this, c = 1;
    for (; b; b >>= 1, a *= a)
      if (b & 1) c *= a;
    return x = c.x, *this;
  }
  modint &operator/=(modint o) { return *this *= o ^= 1000000007 - 2; }
  modint &operator+=(long long o) {
    return x = x + o >= 1000000007 ? x + o - 1000000007 : x + o, *this;
  }
  modint &operator-=(long long o) {
    return x = x - o < 0 ? x - o + 1000000007 : x - o, *this;
  }
  modint &operator*=(long long o) {
    return x = 1ll * x * o % 1000000007, *this;
  }
  modint &operator/=(long long o) {
    return *this *= ((modint(o)) ^= 1000000007 - 2);
  }
  template <class I>
  friend modint operator+(modint a, I b) {
    return a += b;
  }
  template <class I>
  friend modint operator-(modint a, I b) {
    return a -= b;
  }
  template <class I>
  friend modint operator*(modint a, I b) {
    return a *= b;
  }
  template <class I>
  friend modint operator/(modint a, I b) {
    return a /= b;
  }
  friend modint operator^(modint a, long long b) { return a ^= b; }
  friend bool operator==(modint a, long long b) { return a.x == b; }
  friend bool operator!=(modint a, long long b) { return a.x != b; }
  bool operator!() { return !x; }
  modint operator-() { return x ? 1000000007 - x : 0; }
};
long long n, m, a[300005];
modint res, iv[300005], f[300005];
signed main() {
  n = read();
  for (register long long i = (1); i <= (n); ++i) a[i] = read(), m += a[i];
  long long mx = 1e5;
  for (register long long i = (0); i <= (mx); ++i) iv[i] = modint(1) / (m - i);
  for (register long long i = (1); i <= (mx); ++i) iv[i] += iv[i - 1];
  for (register long long i = (1); i <= (mx); ++i)
    f[i] = iv[i - 1] * (m - 1) * (m - i);
  for (register long long i = (1); i <= (n); ++i) res += f[a[i]];
  cout << res.x;
  return 0;
}
