package Practice;

import java.io.BufferedReader;

import java.io.InputStreamReader;

public class B5525 { //IOIOI

public static void main(String[] args) throws Exception {

// TODO Auto-generated method stub

BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

int N = Integer.parseInt(br.readLine());

int M = Integer.parseInt(br.readLine());

String s = br.readLine();

boolean isIOI = false;

int ans = 0, countI = 0, countO = 0;

for(int i = 0; i < M; i++) {

if(s.charAt(i) == 'O' && countI == countO + 1) {

countO++;

continue;

}

if(s.charAt(i) == 'O') {

countI = 0;

countO = 0;

isIOI = false;

continue;

}

if(s.charAt(i) == 'I' && countI == countO) {

countI++;

if(!isIOI && countI == N + 1) {

isIOI = true;

ans++;

}

else if(isIOI) ans++;

continue;

}

if(s.charAt(i) == 'I') {

countI = 1;

countO = 0;

isIOI = false;

continue;

}

}

System.out.println(ans);

}

}