#!/usr/bin/env python3

# Challenge 160
#
# TASK #2 > Equilibrium Index
# Submitted by: Mohammad S Anwar
# You are give an array of integers, @n.
#
# Write a script to find out the Equilibrium Index of the given array, if found.
#
# For an array A consisting n elements, index i is an equilibrium index if the
# sum of elements of subarray A[0...i-1] is equal to the sum of elements of
# subarray A[i+1...n-1].
#
#
# Example 1:
# Input: @n = (1, 3, 5, 7, 9)
# Output: 3
#
# Example 2:
# Input: @n = (1, 2, 3, 4, 5)
# Output: -1 as no Equilibrium Index found.
#
# Example 3:
# Input: @n = (2, 4, 2)
# Output: 1

import sys

def equilibrium_index(n):
    for i in range(1, len(n) - 1):
        left = sum(n[0:i])
        right = sum(n[i + 1:])
        if left == right:
            return i
        if left > right:
            return -1
    return -1

print(equilibrium_index(list(map(int, sys.argv[1:]))))