1163A-Eating Soup

#include <iostream>

#include<vector>

#include<string>

#include<math.h>

/***** S. M. Sabiul Hajjaj Sabit *****/

using namespace std;

int main()

{

    int n,m;

    cin>>n>>m;

    if(n-m==0)

    {

        cout<<0<<endl;

    }

    else if(m==0 || m==1)

    {

        cout<<1<<endl;

    }

    else if(m>n/2)

    {

        cout<<n%m<<endl;

    }

    else

    {

        cout<<m<<endl;

    }

}