99 100 100 100 100
 57 83 11 4 93
 99 99 99 99 99
 100 0 0 0 0
 0 1 2 3 4
 93 100 99 90 98
 87 38 19 33 100
 1 1 1 1 1
 0 0 0 0 1
 2 3 4 5 6
 1 2 1 2 3
 0 0 0 0 0
 100 100 100 100 100
 43 83 1 0 23
 43 83 1 100 23
 56 0 0 0 4
 99 98 98 99 100

-1
 -1
 99
 20
 2
 96
 -1
 1
 -1
 4
 -1
 -1
 100
 30
 50
 12
 -1

import java.util.*;
public class CodeForces 
{ 
    public static void main(String[] args)
    {
       
       Scanner sc = new Scanner(System.in);
       int a[]=new int [5];
       int b[]={0,0,0,0,0};        
       int suma=0,sumb=0;
       for(int i=0;i<5;i++)
       { 
           a[i]=sc.nextInt();
           suma+=a[i];
       }
        while(suma>sumb)
        {
            if(suma==sumb)
            {
                
                break;
            }
            else
            {
                sumb=0;
                for(int i=0;i<5;i++)
                {
                    b[i]+=1;
                    sumb+=b[i]; 
                } 
            }
        }
       
           
         if (sumb>suma||suma==0)
             System.out.println("-1");
         else
             System.out.println(b[0]);
    } 
}
