#include<iostream>
using namespace std;

int main(){
	int a[1000010] = {0};
	int n,m,i,x,y;
	cin>>n>>m;
	//标记开关(m次标记)
	for(i = 1;i <= m;i++){
		cin>>x>>y;
		a[x] = 1 - a[x];//取反
		a[y + 1] = 1 - a[y + 1];//结束位置要多标记一位
	} 
	
	int s = 0;
	int r = 0;//正面朝上的个数
	//存储结果数组
	for(i = 1;i <= n;i++){
		s = s + a[i];
		r = r + s % 2;
	}
	
	cout<<r<<endl;
	
}

/**************************************************************
	Problem: 1538
	User: admin
	Language: C++
	Result: Accepted
	Time:998 ms
	Memory:5856 kb
****************************************************************/