#include <iostream>
#include <iomanip>
#include <algorithm>

using ldouble = long double;

void solve() {
    ldouble a, b, c;
    std::cin >> a >> b >> c;

    ldouble ans = 1 - std::min({a, b, c}) / (a + b + c);
    std::cout << std::fixed << std::setprecision(10) << ans << "\n";
}

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

    solve();

    return 0;
}