#include <iostream>
using namespace std;

int main() {
    int n, k;
    cin >> n >> k;

    int students[2][7] = {0};

    for (int i = 0; i < n; i++) {
        int gender, grade;
        cin >> gender >> grade;
        students[gender][grade]++;
    }

    int roomCount = 0;

    for (int g = 0; g < 2; g++) {
        for (int gr = 1; gr <= 6; gr++) {
            if (students[g][gr] > 0) {
                roomCount += (students[g][gr] + k - 1) / k;
            }
        }
    }

    cout << roomCount << endl;
    return 0;
}