#include <bits/stdc++.h>
using namespace std;

int main()
{
	double P, Q, R;
	cin >> P >> Q >> R;

	double mi = min( P, min( Q, R ) );
	double all = P + Q + R;
	double ans = (all - mi) / all;

	cout << fixed << setprecision(12) << ans << endl;
}