13300(방배정)

#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <math.h>
//13300 방배정
using namespace std;
int main(){
	ios::sync_with_stdio(0); 
	cin.tie(0);
	int arr[13] = { 0 };
	int n, k;
	cin >> n >> k;
	for (size_t i = 0; i < n;i++)
	{
		int a, b;
		cin >> a >> b;
		arr[a * 6 + b]++;
	}
	int room = 0;
	for (size_t i = 1; i < 13; i++)
	{
		room = room + arr[i] / k;
		if (arr[i]%k!=0)
		{
			room++;
		}
	}
	cout << room;
}