package com.company;
import java.util.Scanner;
public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String[] input = scanner.nextLine().split(" ");
        int[] numbers = new int[input.length];
        int leftSum = 0;
        int rightSum = 0;
        int divider = 0;
        for (int i = 0; i < input.length; i++) {
            numbers[i] = Integer.parseInt(input[i]);
        }
        for (int i = 0; i < numbers.length; i++) {
            if (i > 0 && leftSum == rightSum) {
                break;
            } else {
                leftSum = 0;
                rightSum = 0;
                divider = 0;
            }
            if (input.length > 1) {
                divider = i + 1;
            }
            for (int j = 0; j < divider; j++) {
                leftSum += numbers[j];
            }
            for (int k = divider + 1; k < input.length; k++) {
                rightSum += numbers[k];
            }
        }
        if (leftSum - rightSum == 0) {
            System.out.println(divider);
        }else{
            System.out.println("no");
        }
    }
}