I read all the posts, collected input test cases posted by people, and passed all of them successfully, but, unfortunately, still i am getting WA#test case 1. Tried everything. But found no clue why my solution is getting WA. Please help me out.

Try this test. It helped me.
2 2
1 2 10
1 2 20
-1

No solution.

Thank you very much. It helped me as well.

Wy answer is "No solution."?
Can you explain?

We can make trip from 1 to 2 with price 10 and back trip from 2 to 1 with cost 20. It's a cycle with minimum cost

I think, it's because of

> Each sightseeing route is a sequence of road numbers y1, …, yk, k > 2.

Pay attention at "k > 2", it tricked me too.