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

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