I found this case
4
0 1 2 2
1 0 2 2
2 2 0 1
2 2 1 0

and realized that my program had a problem.

Now, if you've got a lot of WAs and you really think your program is correct,try this test case.
Answer is 6 4. The original tree with 6 nodes has some non-integer values as distances.

=) Got AC. yay.