#include<bits/stdc++.h>
using namespace std;
const int N=2e5+5;
int la[N],n,m,ans;
int main(){
	freopen("bridge.in","r",stdin);
	freopen("bridge.out","w",stdout);
	scanf("%d%d",&n,&m);
	for(int i = 0;i<=n;i++) la[i]=n+2;
	for(int i = 1;i<=m;i++){
		int u,v; scanf("%d%d",&u,&v);
	    la[u]=min(la[u],v);
	}
	int f=0;
	for(int i = 1;i<=n;i++){
		if(!f){
			la[i]=min(la[i],la[i-1]); f=0;
		}
		if(la[i]==i+1){ans++; f=1; continue;}
		else la[i+1]=min(la[i+1],la[i]);
	}
	printf("%d",ans);
	return 0;
}