Stage: 4 and 5 Challenge Level: 
The numbers on the edges are counted twice.
The reasoning needed here is much the same as for the problem Plum Tree. See the detailed hint for Plum Tree.
alphas. Stage 5 - Reviewed 2012. Networks/Graph Theory. Codes and cryptography. epsilons. Combinatorics. Algorithms. Mathematical reasoning & proof. Working systematically. Inequality/inequalities.
Published February 2003.
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