input: Write a function to print the Fibonacci series up to a given number 'n'. If 'n' is less than 0, print "Invalid input". 
  assert printFibonacciSeries(5)=="0 1 1 2 3 "
  assert printFibonacciSeries(0)==""
  assert printFibonacciSeries(-1)=="Invalid input"
output: def printFibonacciSeries(n):
      if n < 0:
          return "Invalid input"
      if n == 0:
          return ""
      fib_series = [0, 1]
      while fib_series[-1] + fib_series[-2] <= n:
          fib_series.append(fib_series[-1] + fib_series[-2])
      return ' '.join(map(str, fib_series)) + ' '