import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.InputMismatchException;
import java.io.IOException;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 *
 * @author ankur
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        InputReader in = new InputReader(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        TaskC solver = new TaskC();
        solver.solve(1, in, out);
        out.close();
    }

    static class TaskC {
        long mod = (long) 1e9 + 7;

        public void solve(int testNumber, InputReader in, PrintWriter out) {
            int n = in.nextInt();
            char ar[] = new char[n];
            for (int i = 0; i < n; i++) {
                ar[i] = in.readString().charAt(0);
            }
            long dp[][] = new long[n + 1][n + 1];
            for (int i = 0; i < n; i++) {
                dp[n - 1][i] = 1;
            }
            long prev = n;
            for (int i = n - 2; i >= 0; i--) {
                if (ar[i] == 'f') {
                    if (ar[i + 1] == 's') {
                        for (int j = n - 2; j >= 0; j--) {
                            dp[i][j] = dp[i + 1][j + 1];
                        }
                    } else {
                        for (int j = n - 2; j >= 0; j--) {
                            dp[i][j] = dp[i + 1][j + 1];
                        }

                    }
                } else {
                    for (int j = n - 1; j >= 0; j--) {
                        if (prev < 0) {
                            prev += mod;
                        }
                        dp[i][j] = prev;
                        prev = prev - dp[i + 1][j];
                    }
                }
                prev = 0;
                for (int j = 0; j < n; j++) {
                    prev +=... Which one is the correct time complexity of the code snippet: constant, linear, quadratic, cubic, log(n), nlog(n) or NP-hard?