#include <bits/stdc++.h>

using namespace std;

using ll = long long;
using ul = unsigned long;
using ull = unsigned long long;

int main()
{
	ios::sync_with_stdio(false);
	cin.tie(nullptr);

	int p, q, r;
	cin >> p >> q >> r;

	double res = max({ p + q,q + r,r + p }) / (double)(p + q + r);

	cout << fixed << setprecision(15) << res << "\n";

	return 0;
}