#include <bits/stdc++.h>
using namespace std;
#define int long long
typedef pair<int,int> P;
int INF = 1e18+7;
int mod = 1e9+7;
int dx[4] = {1, 0, -1, 0};
int dy[4] = {0, 1, 0, -1};
signed main() {
    double P,Q,C;
    cin >> P >> Q >> C;
    double sum = P+Q+C;
    double mx = max({P,Q,C});
    cout << fixed << setprecision(20) << max(mx/sum,(sum-mx)/sum) << endl;
}