#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define MAXN 200010
inline ll read(){
	ll x=0,f=1;
	char c=getchar();
	while(c<'0'||c>'9'){
		if(c=='-')f=-1;
		c=getchar();
	}
	while(c>='0'&&c<='9'){
		x=x*10+c-'0';
		c=getchar();
	}
	return x*f;
}
ll lst[MAXN];
ll ans,n,m;
int main(){
	freopen("bridge.in","r",stdin);
	freopen("bridge.out","w",stdout);
	n=read(),m=read();
	for(int i=1;i<=n;i++)lst[i]=n+2;
	for(int i=1;i<=m;i++){
		ll a=read(),b=read();
		lst[a]=min(lst[a],b);
	}
	for(int i=1;i<=n;i++){
		if(lst[i]==i+1)ans++;
		else lst[i+1]=min(lst[i+1],lst[i]);
	}
	cout<<ans;
	return 0;
}