that's so strange
I`m getting WA on test 1
my code prints for sample input #1
1
2
3
1
2
1 2
1 3
1 5
2 3
and for second :
1
2
1
2
1 2
1 4
2 3
3 4
please help me !
thank you

Accepted after reread the problem statement
problem says :
"Each student is assigned one classroom he is responsible for"
My output was wrong for test #1

In your output for sample #1 student no. 4 is never on duty!

"Each of the students should be on duty at least once during these [m] days."