using System;
					
public class Program
{
	public static void Main()
	{
		int[] A = {-7, 1, 5, 2, -4, 3, 0};
		
		int length = A.Length;
		
		int sum1=0, sum2=0;
		
		
		if(A.Length < 3)
		{
			System.Console.Write("-1");
		}
		else
		{
			for(int i = 1; i<length; i++)
			{
				for(int j=0; j<length; j++)
				{
				System.Console.Write("j:"+j+" "+"i:"+i+" ");
					if(A[j] < A[i])
					{
						sum1 +=A[j];
					}
					
					if(A[j] > A[i] && A[j]<length)
					{
						sum2 +=A[j];
					}	
				}
				if(sum1 ==sum2)
				{
					System.Console.Write(i);
					break;
				}	
			
			}
			
		}
		
	}
}