import java.io.BufferedReader;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.math.BigInteger;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.PriorityQueue;
import java.util.Queue;
import java.util.Scanner;
import java.util.Stack;
import java.util.StringTokenizer;
import java.util.TreeSet;
import java.util.concurrent.LinkedBlockingDeque;

import javax.swing.border.Border;

public class a {

	public static long mod = (long) Math.pow(10, 9) + 7;
	public static int k = 0;

	private static class node {
		long min;
		long num;
		long gcd;

		node(long m, long n, long g) {
			min = m;
			num = n;
			gcd = g;
		}

	}

	public static class point implements Comparable<point> {
		long x;
		long y;
		long b;

		point(long x, long y, long b) {
			this.x = x;
			this.y = y;
			this.b = b;
		}

		@Override
		public int compareTo(point o) {
			if (k == 0)
				return (int) (o.x - x);
			else
				return (int) (y - o.y);

		}
	}

	public static int ch(long y) {
		int r = Long.bitCount(y);
		return r;
	}

	public static long gcd(long x, long y) {
		if (y == 0)
			return x;

		return gcd(y, x % y);
	}

	public static boolean ch[];
	public static ArrayList<Integer> prime;
	public static Queue<Integer> pp;

	public static void sieve(int k) {
		ch[0] = ch[1] = true;

		for (int i = 2; i <= k; i++) {
			if (!ch[i]) {
				prime.add(i);
				pp.add(i);
				for (int j = i + i; j <= k; j += i) {
					ch[j] = true;
				}
			}
		}

	}

	public static long pw(int x, int power, int mod) {
		if (power == 1)
			return x % mod;
		else if (power % 2 == 0) {
			return pw((x % mod * x % mod) % mod, power / 2, mod);
		} else {
			return (pw(x, power - 1, mod) % mod * x % mod) % mod;
		}
	}

	public static void main(String[] args) throws IOException {
		BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
		StringBuilder qq = new StringBuilder();
		PrintWriter out = new PrintWriter(new OutputStreamWriter(System.out));
		int p = Integer.parseInt(in.readLine());
		String y = in.readLine();
		int last = 0;
		for (int i = 0; i < y.length(); i++) {
			if (y.charAt(i) == 'I')
				last = i;
		}
		int ans=0;
		for (int i = last; i < y.length(); i++) {
				if(y.charAt(i)!='F')
					ans++;
		}
		System.out.println(ans);
		out.close();

	}
}