#include <stdio.h>
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace atcoder;
using mint = modint998244353;
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf32 1000000001
#define Inf64 1000000000000000001
vector<pair<int,int>> lr;
int check(long long k){
	
	int n = lr.size();
	int cp = 0;
	priority_queue<int,vector<int>,greater<int>> Q;
	rep(i,n){
		int cur = k + i;
		while(cp!=n){
			if(lr[cp].first <= cur){
				Q.push(lr[cp].second);
				cp++;
			}
			else break;
		}
			
		if(Q.size()==0)return -1;
		if(Q.top()<cur)return 1;
		Q.pop();
	}
	return 0;
	
	
}
int main(){
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	
	int n;
	cin>>n;
	lr.resize(n);
	rep(i,n)cin>>lr[i].first>>lr[i].second;
	sort(lr.begin(),lr.end());
	
	long long ans = 0;
	
	{
		long long ok = -1,ng = 2000000000;
		while(ng-ok>1LL){
			
			long long mid = (ok+ng)/2;
			if(check(mid)<=0)ok = mid;
			else ng =mid;
		}
		ans += ok;
	}
	
	{
		long long ok = -1,ng = 2000000000;
		while(ng-ok>1LL){
			
			long long mid = (ok+ng)/2;
			if(check(mid)<=-1)ok = mid;
			else ng =mid;
		}
		ans -= ok;
	}
	cout<<ans<<endl;
	
	
	return 0;
}