#include<bits/stdc++.h> using namespace std; int main(){ double f; cin>>f; double c=5*(f-32)/9; cout<<fixed<<setprecision(5)<<c; return 0; }

#include<bits/stdc++.h>
using namespace std;
int main(){
  double c,f;
  cin>>f;
  c=5*(f-32)/9;
  printf("%.5f",c);
  return 0;
}