#include <iostream>
#include <cstdio>

using namespace std;

int main(){
  int n,m;

  cin >> n >> m;

  if(n == 2){
    printf("%d¥n",max(1, n/m));
    return 0;
  }

  if(n > m){
    puts("-1");
  }else{
    int ans = (m+n-1)/n;
    printf("%d\n",ans);
  }

  return 0;
}