#include <stdio.h>
#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf 1000000000



int main(){

	double a,b,c;
	cin>>a>>b>>c;
	
	cout<<fixed<<setprecision(10)<<1.0 - min({a,b,c}) / (a+b+c)<<endl;

	return 0;
}