You need to find the number that occurs an odd amount of times, not the maximum amount of times.

You are failing this test:

array = [1, 1, 2, -2, 5, 2, 4, 4, -1, -2, 5]

Number of occurences = {1: 2, 2: 2, 4: 2, 5: 2, -1: 1, -2: 2}

-1 has an **odd** number of occurences, therefore you should return -1.