#include<bits/stdc++.h>
using namespace std;

bool mapp[1005][1005];
bool tem;
int n,m;
int a,b;
int ans;


int main(){
	freopen("tongzhuo.in","r",stdin);
	freopen("tongzhuo.out","w",stdout);
	cin >> n >> m;
	while(cin >> a){
		cin >> b;
		mapp[a][b]=1;
	}
	for(int i=0;i<=n-m;i++){
		tem=0;
		for(int j=n-m+1;j<=n;j++){
			if(mapp[i][j]==1){
				tem=1;
			for(int o=n-m+1;o<=n;o++){
				mapp[j][o]=0;
			}
			break;
			}
		}
		if(tem){
			ans++;
		}
	}
	cout <<ans;
	return 0;
}