using System;
using System.Linq;
using System.Collections.Generic;

namespace _11_Еxc_EqualSum
{
    class Program
    {
        static void Main(string[] args)
        {
            List<int> arrInput = Console.ReadLine().Split(' ').Select(int.Parse).ToList();
            bool ifExists = true;
            for (int i = 0; i < arrInput.Count(); i++)
            {
                if (arrInput.Take(i).Sum() == arrInput.Skip(i + 1).Sum())
                {
                    Console.WriteLine(i);
                    ifExists = false;
                    break;
                }
            }
            if (ifExists) Console.WriteLine("no");
        }
    }
}