source_code: import java.util.*;
  public class A{
         
         public static int mod = 1000000007;
         
         public static void main(String args[]){
                Scanner sc = new Scanner(System.in);
                int n = sc.nextInt();
                char s[] = new char[n];
                for(int i = 0; i < n; i++)
                       s[i] = sc.next().charAt(0);
                int dp[][] = new int[5001][5001];
                int sum[][] = new int[5001][5001];
                dp[0][0] = 1;
                sum[0][0] = 1;
                for(int i = 1; i < n; i++){
                       for(int j = n - 1; j >= 0; j--){
                              if(s[i-1] == 'f' && j > 0){
                                     dp[i][j] = dp[i-1][j-1] % mod;
                              }else if(s[i-1] == 's'){
                                     dp[i][j] = sum[i-1][j] % mod;
                              }
                              sum[i][j] = (sum[i][j+1] + dp[i][j]) % mod;
                       }
                }
                System.out.println(sum[n-1][0]);
         }
  }