#include<bits/stdc++.h>
using namespace std;

int main(){
    int n,d;
    cin>>n>>d;
    if(n==d)cout<<0<<endl;
    else if(n%d==1)cout<<n-1<<endl;
    else if(n%d==0)cout<<n/d-1<<endl;
    else cout<<n/(n%d)-1<<endl;
}