#include<bits/stdc++.h>

using namespace std;

int main()

{

double n,m;
cin >> n >> m;
cout << fixed << setprecision(2) << n-m*0.8; 
return 0;
}

#include<bits/stdc++.h>

using namespace std;

int main()

{

double n,m;
cin >> n >> m;
cout << fixed << setprecision(2) << n-m*0.8;
\
return 0;
}

#include<bits/stdc++.h>

using namespace std;

int main()

{

double n,m;
cin >> n >> m;
cout << fixed << setprecision(2) << n-m*0.8; 
return 0;

}