#include <bits/stdc++.h>
using namespace std;
int main() {
    double F;
    cin >> F;

    double C = 5.0 * (F - 32) / 9.0;

    printf("%.5lf",C);

    return 0;
}

#include <iostream>
#include <iomanip>
using namespace std;

int main() {
    double F;
    cin >> F;

    double C = 5.0 * (F - 32) / 9.0;

    cout << fixed << setprecision(5) << C << endl;

    return 0;
}