Thanks in advance for attention to this 5-year old problem.

1266D - Decreasing Debts

Example input:

5 4
1 2 2
4 1 4
4 2 4
3 1 4

Example output: (generated by Accepted submissions / editorial algorithm, but I do not understand. Can be verified by 67085154)

3
4 1 6
4 2 2
3 2 4

I don't see a way to increase the edge 4-1 to a weight 6, by the operations described in the problem statement.