[[0,2],[0,3],[1,2],[1,3],[1,4],[2,4]]

["ATL","PEK","LAX","DXB","HND"]

["ATL","DXB","HND","LAX"]

4

[[1,0],[2,0],[3,0],[2,1],[3,1],[3,2]]

["ATL","PEK","LAX","DXB"]

["ABC","DEF","GHI","JKL","MNO","PQR","STU","VWX"]

6

[[0,1],[1,2],[2,3],[3,4],[4,5]]

["ATL","PEK","LAX","ATL","DXB","HND"]

["ATL","DXB","HND","DXB","ATL","LAX","PEK"]