# -*- coding: utf-8 -*-
"""Challenge 3 - Intermediate Problem-Khalid AlHarbi

Automatically generated by Colab.

Original file is located at
    https://colab.research.google.com/drive/1_2HkSGM815VLsizjxyZBUmFIz5FEe2D8
"""

def single_number(nums):
    unique_num = 0
    for num in nums:
        unique_num ^= num
    return unique_num

#Examples of use
print(single_number([2, 2, 1]))    # Output: 1
print(single_number([4, 1, 2, 1, 2]))  # Output: 4
print(single_number([1]))          # Output: 1