input: Write a function to print a staircase of height 'n' where n is an integer. The staircase should be right-aligned and consist of hashes ('#') with spaces on the left. If the input n is less than 1, the function should print nothing.
  assert staircase(5)==None
  assert staircase(3)==None
  assert staircase(0)==None
  assert staircase(7)==None
  assert staircase(1)==None
output: def staircase(n):
      if n < 1:
          return
      for i in range(1, n + 1):
          print(' ' * (n - i) + '#' * i)