#include <bits/stdc++.h>
using namespace std;
const int mod = 1e9 + 7;
int n;
char s[5001];
int dp[5001][5001];
int main() {
  scanf("%d", &n);
  for (int i = 1; i <= n; ++i) {
    scanf("\n%c", &s[i]);
  }
  dp[1][0] = 1;
  for (int j = 1; j <= n; ++j) {
    dp[1][j] = 0;
  }
  for (int i = 2; i <= n; ++i) {
    if (s[i - 1] == 'f') {
      for (int j = 1; j <= n; ++j) {
        dp[i][j] = dp[i - 1][j - 1];
      }
    } else {
      int x = 0;
      for (int j = n; j >= 0; --j) {
        x += dp[i - 1][j];
        if (x >= mod) {
          x -= mod;
        }
        dp[i][j] = x;
      }
    }
  }
  int res = 0;
  for (int i = 0; i <= n; ++i) {
    res += dp[n][i];
    if (res >= mod) {
      res -= mod;
    }
  }
  cout << res << "\n";
  return 0;
}
