#include <bits/stdc++.h>
using namespace std;
long long dp[5005][5005], bad[30][5005], pre[5005];
const long long MOD = 1e9 + 7;
long long fact[5005];
long long qikpow(long long a, long long b) {
  if (!b) {
    return 1;
  }
  long long ret = qikpow(a, b / 2);
  ret *= ret;
  ret %= MOD;
  if (b & 1) {
    ret *= a;
    ret %= MOD;
  }
  return ret;
}
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  int N;
  cin >> N;
  fact[0] = 1;
  dp[0][0] = 1;
  pre[0] = 1;
  for (int i = 1; i <= N; i++) {
    char c;
    cin >> c;
    fact[i] = (fact[i - 1] * i) % MOD;
    for (int k = 1; k <= i; k++) {
      dp[i][k] = pre[k - 1];
      dp[i][k] = (dp[i][k] - bad[c - 'a'][k - 1] + MOD) % MOD;
      dp[i][k] = (dp[i][k] - bad[c - 'a'][k] + MOD) % MOD;
    }
    for (int k = 1; k <= i; k++) {
      bad[c - 'a'][k] = (bad[c - 'a'][k] + dp[i][k]) % MOD;
      pre[k] = (pre[k] + dp[i][k]) % MOD;
    }
  }
  long long ans = 0;
  for (int i = 1; i <= N; i++) {
    ans += pre[i] * fact[N - 1] % MOD *
           qikpow(fact[i - 1] * fact[N - i] % MOD, MOD - 2) % MOD;
    ans %= MOD;
  }
  cout << ans;
}
