part2

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The bridge you've built isn't long enough; you can't jump the rest of the way.

In the example above, there are two longest bridges:

0/2--2/2--2/3--3/4
0/2--2/2--2/3--3/5
Of them, the one which uses the 3/5 component is stronger; its strength is 0+2 + 2+2 + 2+3 + 3+5 = 19.

What is the strength of the longest bridge you can make? If you can make multiple bridges of the longest length, pick the strongest one.