#include<bits/stdc++.h>
using namespace std;
int main(){
    double a,b;
    cin>>a>>b;
    int x=a/b;
    cout<<a-x*b<<endl; 
    return 0;
}

#include <bits/stdc++.h>
using namespace std;
int main(){
	double a,b;
	cin >> a >> b;
    int  c = a/b;
    cout << a - c*b;
	return 0;
}