#include<bits/stdc++.h>
using namespace std;
int main()
{
	double a,b,ans;
	int k;
	scanf("%lf %lf",&a,&b);
	k=a/b;
	cout<<a-k*b;
	return 0;
}

#include<bits/stdc++.h>
using namespace std;
const int N=5e5+5,INF=0x3f3f3f3f;
typedef long long LL;
double a,b;
int main()
{
	cin>>a>>b;
	cout<<a-(int)(a/b)*b;
	return 0;
}

#include<iostream using namespace std; int main() { double a,b; int k; cin>>a>>b; k=a/b; cout<<a-k*b; return 0; }

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