input: Write a python function to search for a number in an array and return its index.
  assert search([22, 54, 71, 12, 7, 37], 12) == 3
  assert search([22, 54, 71, 12, 7, 37], 7) == 4
  assert search([22, 54, 71, 12, 7, 37], 100) == -1
output: def search(arr, num):
      try:
          return arr.index(num)
      except ValueError:
          return -1