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txxtxttxxttxtxx
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myw
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isssisssss
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ff
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z

27824
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#include <bits/stdc++.h>
using namespace std;
template <class T>
inline T BM(T p, T e, T M) {
  long long int ret = 1;
  for (; e > 0; e >>= 1) {
    if (e & 1) ret = (ret * p) % M;
    p = (p * p) % M;
  }
  return (T)ret;
}
template <class T>
inline T gcd(T a, T b) {
  if (b == 0) return a;
  return gcd(b, a % b);
}
template <class T>
inline T mdINV(T a, T M) {
  return BM(a, M - 2, M);
}
template <class T>
inline T PW(T p, T e) {
  long long int ret = 1;
  for (; e > 0; e >>= 1) {
    if (e & 1) ret = (ret * p);
    p = (p * p);
  }
  return (T)ret;
}
template <class T>
string NTS(T Number) {
  stringstream ss;
  ss << Number;
  return ss.str();
}
template <class T>
T stringtonumber(const string &Text) {
  istringstream ss(Text);
  T result;
  return ss >> result ? result : 0;
}
template <class T>
bool ISLEFT(T a, T b, T c) {
  if (((a.first.first - b.first.first) * (b.second.second - c.second.second) -
       (b.first.first - c.first.first) * (a.second.second - b.second.second)) <
      0.0)
    return 1;
  else
    return 0;
}
char a[5005];
int n;
int dp[5005][5005];
int ind[5005ll][27];
int go(int in, int last) {
  if (in > n) {
    return 1;
  }
  int &ret = dp[in][last];
  if (ret != -1) return ret;
  ret = 0;
  for (int j = 1; j <= 26; j++) {
    if (ind[last][j] <= n) {
      ret += go(in + 1, ind[last][j]);
      if (ret >= 1000000007) ret -= 1000000007;
    }
  }
  return ret;
}
int main() {
  scanf("%d", &n);
  scanf("%s", a + 1);
  for (int i = 1; i <= 26; i++) ind[n + 1][i] = n + 1;
  for (int i = n; i >= 1; i--) {
    for (int j = 1; j <= 26; j++) ind[i][j] = ind[i + 1][j];
    int first = a[i] - 'a' + 1;
    ind[i][first] = i;
  }
  dp[0][1] = 1;
  for (int i = 1; i <= n; i++) {
    for (int j = 1; j <= n; j++) {
      for (int k = 1; k <= 26; k++) {
        if (ind[j][k] <= n) {
          dp[i][ind[j][k]] += dp[i - 1][j];
          if (dp[i][ind[j][k]] >= 1000000007) dp[i][ind[j][k]] -= 1000000007;
        }
      }
    }
  }
  int ans = 0;
  for (int i = 1; i <= n; i++) {
    ans += dp[n][i];
    if (ans >= 1000000007) ans -= 1000000007;
  }
  printf("%d", ans);
  return 0;
}
