[[練習問題]]
 #!/usr/bin/python
 # -*- coding: utf-8 -*-
 import sys
 def fibo(n):
     x, y = 0, 1
     for i in xrange(n):
         x, y = y, x+y
     return x
 
 n = int(sys.argv[1])
 print('{0}: {1}'.format(n, fibo(n)))