#include<bits/stdc++.h>
using namespace std;
stack<int>s[8];
int main(){
	int n,p;
	cin >> n >> p;
	int cnt = 0;
    while (n--){
    	int i,j;
    	cin >> i >> j;
		while(s[i].size() != 0 && s[i].top() > j){
			s[i].pop();
			cnt++;
		}
		if (s[i].size() != 0) {
			if (s[i].top() == j) continue;
			cnt++;
			s[i].push(j);
		}else{
			s[i].push(j);
			cnt++;
		}
		s[i].push(j);
		cnt++;
	}
	cout << cnt;
}

WA on all