A regional planner wants to open a quiet retreat in one of n towns 0 .. n-1. Roads are
undirected: roads[i] = [u, v, km] (km >= 0, parallel roads possible). A town's crowd is the
number of other towns whose shortest road distance to it is at most radius.
Return the town with the smallest crowd. If several towns tie, return the smallest label.
Examples
Input: n = 4, roads = [[0,1,3],[1,2,1],[2,3,4],[0,3,10]], radius = 4
Output: 3
Explanation: crowds are 0 -> {1,2}, 1 -> {0,2}, 2 -> {0,1,3}, 3 -> {2}. Town 3 is quietest.
Input: n = 3, roads = [], radius = 5
Output: 0
Explanation: every crowd is 0; the smallest label wins.
Constraints
1 <= n <= 100,0 <= len(roads) <= n * (n - 1),0 <= km, radius <= 10**4- Target
O(n**3)time.
Goals
- Compute all-pairs shortest distances on a small undirected graph
- Count neighbours within a distance limit for each node
- Break ties by the stated rule