input: Write a function to find the maximum product of any two positive numbers in an array.
  assert maxProduct([6, -3, -10, 0, 2]) == 12
  assert maxProduct([1, 2, 3, 4, 5]) == 20
  assert maxProduct([0, -1, -2, -3]) == 0
output: def maxProduct(arr):
      max1 = max2 = 0
      for num in arr:
          if num > max1:
              max2 = max1
              max1 = num
          elif num > max2:
              max2 = num
      return max1 * max2