#include "bits/stdc++.h"

//#include <atcoder/all>

using namespace std;
//using namespace atcoder;

//#define int long long
#define ll long long

ll INF = (1LL << 60);
int mod = 1000000007;

using P = pair<int, int>;

signed main() {
	vector<int>A(3); for (int i = 0; i < 3; i++)cin >> A[i];
	sort(A.rbegin(), A.rend());
	double sum = 0;
	sum += A[0] + A[1] + A[2];
	double ans = (A[0] + A[1])/sum;
	cout << fixed << setprecision(15) << ans << endl;
	return 0;
}