I hope these tests will be useful for you :)
4 5 0
3 4
1 2
3 1
2 4

and

7 7 0
1 2
1 3
2 4
2 5
3 6
3 7
4 7

The output must be 0 in both cases, but if you've done something wrong, it can be -1. Make sure your determination of connected components isn't wrong.

you gave the wrong 1 test
here's the correct
4 4 0
3 4
1 2
3 1
2 4
answer : 0