import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        double total = 0;
        double[] rates = new double[3];
        for (int i = 0; i < 3; i++) {
            rates[i] = sc.nextInt();
            total += rates[i];
        }
        Arrays.sort(rates);
        System.out.println(Math.max(1 - rates[0] / total, rates[2] / total));
    }
}