#include <iostream>
#include <cstdio>
#include <algorithm>
#include <map>
using namespace std;
const int nmax=10000086;
int n,m;
int tmpl,tmpr;
map<int,int > mapp;
class poi
{
public:
	int l,r;
}save[nmax];
int s=0;
int tmpmax=0;
int cnt=0;
int ans=0;
int tmpv=0;
int tmp[nmax];
int state[nmax];
bool tag[nmax]={0};
void PreDo()
{
	scanf("%d%d",&n,&m);
	for(int i=1;i<=m;i++)
	{
		scanf("%d%d",&tmpl,&tmpr);
		if(tmpr-1>tmpmax)
			tmpmax=tmpr;
		save[i].l=tmpl;
		save[i].r=tmpr;
		tmp[++s]=tmpl;
		tmp[++s]=tmpr;
	}
}
void Dis()
{
	sort(tmp+1,tmp+s+1);
	mapp[tmp[1]]=1;
	for(int i=2;i<=s;i++)
	{
		
		if(!mapp[tmp[i]])
		{
			if(tmp[i]-tmp[i-1]>1)
				mapp[tmp[i]]=mapp[tmp[i-1]]+2;
			else
				mapp[tmp[i]]=mapp[tmp[i-1]]+1;
		}
	}
}

void DrownProof()
{
	cnt=0;
	tag[0]=1;
	for(int i=1;i<=m;i++)
	{	
		cnt++;
		for(int j=mapp[save[i].l];j<=mapp[save[i].r];j++)
			state[j]=cnt;
	}
	for(int i=1;i<=n;i++)
		if(tag[state[i]]==0)
		{
			ans++;
			tag[state[i]]=1;
		}
	printf("%d\n",ans);
}
int main()
{
	freopen("ha14d.in","r",stdin);
	freopen("ha14d.out","w",stdout);
	PreDo();
	Dis();
	DrownProof();
	return 0;
}