#include <iostream>
#include <iomanip>
using namespace std;
int main(){
double F,C;
cin>>F;
C=5*(F-32)/9;
cout<<fixed<<setprecision(5);
cout<<C;
return 0;
}
#include <iostream>
#include <iomanip>
using namespace std;
int main(){
double F,C;
cin>>F;
C=5*(F-32)/9;
cout<<fixed<<setprecision(5);
cout<<C;
return 0;
}