import java.util.*;
public class Test10 {
  public static void main(String[] args){
    Scanner sc=new Scanner(System.in);
    String[] line;
    line=sc.nextLine().split(" ");
    double[] data=new double[3];
    double sum=0;
    for(int i=0;i<3;i++){
      data[i]=Double.parseDouble(line[i]);
      sum+=data[i];
    }
    Arrays.sort(data);
    double p=1-(data[0]/sum);
    System.out.println(p);
    sc.close();
  }
}