//minamoto

 #include<set>

 #include<iostream>

 #include<cstdio>

 #define ll long long

 #define IT set<node>::iterator

 using std::set;

 #define getc() (p1==p2&&(p2=(p1=buf)+fread(buf,1,1<<21,stdin),p1==p2)?EOF:*p1++)

 char buf[<<],*p1=buf,*p2=buf;

 ll read(){

     #define num ch-'0'

     char ch;bool flag=;ll res;

     while(!isdigit(ch=getc()))

     (ch=='-')&&(flag=true);

     for(res=num;isdigit(ch=getc());res=res*+num);

     (flag)&&(res=-res);

     #undef num

     return res;

 }

 struct node{

     ll l,r;mutable int v;

     node(ll L,ll R=-,int V=):l(L),r(R),v(V){}

     inline bool operator <(const node &b)const

     {return l<b.l;}

 };set<node> s;

 IT split(ll pos){

     IT it=s.lower_bound(node(pos));

     if(it!=s.end()&&it->l==pos) return it;

     --it;int l=it->l,r=it->r;ll v=it->v;

     s.erase(it),s.insert(node(l,pos-,v));

     return s.insert(node(pos,r,v)).first;

 }

 void assign(ll l,ll r){

     IT itr=split(r+),itl=split(l);

     s.erase(itl,itr),s.insert(node(l,r,));

 }

 ll sum(ll l,ll r){

     IT itr=split(r+),itl=split(l);ll res=;

     for(;itl!=itr;++itl) res+=itl->v?itl->r-itl->l+:;

     return res;

 }

 int main(){

 //    freopen("testdata.in","r",stdin);

     int n=read();s.insert(node(,1e17+,));

     while(n--){

         ll l=read(),r=read();assign(l,r);

     }

     printf("%lld\n",sum(,1e17));

     return ;

 }