#include<stdio.h>
#include<stdlib.h>
#include<algorithm>
#include<vector>
using namespace std;
vector< pair<int, int> > v;

int cnt[110];
int main(){
	int i, n, a, b, ans=0, j, m;
	scanf("%d %d", &n, &m);
	for(i=0;i<m;i++){
		scanf("%d %d", &a, &b);
		v.push_back({b,a});
	}

	ans = 0;
    sort(v.begin(), v.end());

    for(i=0;i<m;i++){
        pair<int, int> k = v[i];
        for(j=0;j<n;j++){
            if(cnt[j] <= k.second){
                cnt[j] = k.first;
                ans++;
            }
        }

    }

	printf("%d",ans);
}