Lone number

You are given a list consisting of $n$ integers. $n-1$ of the integers are equal and one has a different value. Your task is to determine what the different integer is.

The time complexity of the algorithm should be $O(n)$. You may assume that $n>2$.

In a file onlyone.py, implement a function find that returns the desired integer.

def find(t):
    # TODO

if __name__ == "__main__":
    print(find([1,1,2,1])) # 2
    print(find([4,5,5])) # 4
    print(find([1,1,1,1,2])) # 2
    print(find([8,8,5,8,8])) # 5