input: Write a python function to concatenate two strings and capitalize the first letter of the result.
  assert concat_and_capitalize('python', 'programming') == 'Pythonprogramming'
  assert concat_and_capitalize('hello', 'world') == 'Helloworld'
  assert concat_and_capitalize('good', 'morning') == 'Goodmorning'
output: def concat_and_capitalize(str1, str2):
      result = str1 + str2
      return result.capitalize()