Online Judge	Problem Set	Authors	Online Contests	User
Web Board Home Page F.A.Qs Statistical Charts	Problems Submit Problem Online Status Prob.ID:	Register Update your info Authors ranklist	Current Contest Past Contests Scheduled Contests Award Contest	User ID: Password:   Register

input
10 10
1 3
2 4
3 5
4 6
5 7
6 8
7 9
8 10
9 10
10 10

output
4

1 3
4 6
7 9
9 10

Home Page   Go Back  To top

All Rights Reserved 2003-2013 Ying Fuchen,Xu Pengcheng,Xie Di
Any problem, Please Contact Administrator