rt

#include<iostream> 
int n,m,l,r,i,p,o[200010];main(){std::cin>>n>>m;p=n;while(m--){std::cin>>l>>r;for(i=l;i<=r;){if(o[i])i=o[i];else{p--;if(o[r+1])o[i]=o[r+1];else o[i]=r+1;i++;}}printf("%d\n",p);}}