很多人在这都会有printf,但这里需要用cout！

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

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

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

int main(){ long double a,b,s; cin>>a>>b; s=a-((int)(a/b)*b); cout<<s; return 0; }