public class MyClass {
    public static void main(String args[]) {
        java.util.Scanner scanner = new java.util.Scanner(System.in);
        String[] numberStrs = scanner.nextLine().split(" ");
        int[] numbers = new int[numberStrs.length];
        boolean yn = false;
        for(int i = 0;i < numberStrs.length;i++)
        {
            numbers[i] = Integer.parseInt(numberStrs[i]);
        }
        for (int i = 0; i < numbers.length;i++) {
            yn = checkLeftRightSum(i,numbers);
            if (yn) {
                System.out.println(i);
                break;
            }
        }
        if (!yn) {
            System.out.println("no");
        }
    }
    public static boolean checkLeftRightSum(int index, int[] numbers) {
        int leftSum = 0;
        int rightSum = 0;
        if (index == 0) {
            leftSum = 0;
        }
        if (index == numbers.length -1) {
            rightSum = 0;
        }
        for (int i = index;i >= 0; i--) {
            leftSum += numbers[i];
        }
        for (int i = index; i < numbers.length;i++) {
            rightSum += numbers[i];
        }
        return leftSum == rightSum;
    }
}