I submitted a solution for the problem: E. Bertown roads My submission is: 289121858

ideone Link of the same submission: https://ideone.com/Pn4Wdh

The checker comment I got is:

wrong output format Unexpected end of file — int32 expected

for the testcase:

6 8
1 2
2 3
1 3
4 5
4 6
5 6
2 4
3 5

But if I run the same code with same input on online compilers and my machine, it produces correct output. You can even check the ideone link I provided, even this one producing the correct output.