n,m=map(int,input().split())
remains=n-m*0.8
print('%.2f' %remains)

#include<bits/stdc++.h>
using namespace std;
int main(){
    double n,m,a;
    cin>>n>>m;
    a=n-m*0.8;
    printf("%0.2lf",a);
    return 0;
}