import java.io.PrintWriter;
import java.util.Arrays;
import java.util.Scanner;
import java.util.Stack;

class Main {
	public static void main(String[] $) {
		new Main().run();
	}
	
	void run() {
		Scanner sc=new Scanner(System.in);
		int[] a=new int[3];
		for (int i=0;i<3;++i) a[i]=sc.nextInt();
		Arrays.sort(a);
		System.out.println(1-a[0]/(a[0]+a[1]+a[2]+.0));
		
		
	}
	
	void tr(Object...objects) {System.out.println(Arrays.deepToString(objects));}
}