At: en inj 1 2 1 2 1
1. n: 

2. m: 
3. 0 < m
4.
l1,l2:
n*. ||l1|| = m-1 & ||l2|| = m-1 
en(l1) = en(l2) 
l1 = l2
5. l1:
n*
6. l2:
n*
7. u:
n
8. v:
n*
||u.v|| = m & ||nil|| = m 
en(u.v) = en(nil) 
u.v = nil
By: Reduce 0
Generated subgoals:None
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