problem with "elif"

[Pjotr]

Hello!
I started learning Python, using Python 2.1.1 and Ivan Laningham's
book "Teach yourself Python...".  I have a problem with instruction
"elif":
>>> y = 1900
>>> leap = "no"
>>> if y % 400 == 0 :
           leap = "yes"
       elif y % 100 == 0 :
            
IndentationError: unindent does not match any outer indentation level
(line 3)
>>> 

What's up? This example is from Laningham's book and everything should
be OK. Please help me!
-- 
Best regards
Pjotr
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