CSES - School Dance
  • Time limit: 1.00 s
  • Memory limit: 512 MB

There are n boys and m girls in a school. Next week a school dance will be organized. A dance pair consists of a boy and a girl, and there are k potential pairs.

Your task is to find out the maximum number of dance pairs and show how this number can be achieved.


The first input line has three integers n, m and k: the number of boys, girls, and potential pairs. The boys are numbered 1,2,\dots,n, and the girls are numbered 1,2,\dots,m.

After this, there are k lines describing the potential pairs. Each line has two integers a and b: boy a and girl b are willing to dance together.


First print one integer r: the maximum number of dance pairs. After this, print r lines describing the pairs. You can print any valid solution.


  • 1 \le n,m \le 500
  • 1 \le k \le 1000
  • 1 \le a \le n
  • 1 \le b \le m



3 2 4
1 1
1 2
2 1
3 1


1 2
3 1