#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

int check(vector<int> l,vector<int> r,long long k){
	map<int,vector<int>> mp;
	rep(i,l.size()){
		mp[l[i]].push_back(r[i]);
	}
	int n = l.size();
	priority_queue<int,vector<int>,greater<int>> Q;
	rep(i,n){
		int cur = k + i;
		while(mp.size()>0){
			auto it = mp.begin();
			if(it->first <= cur){
				rep(j,it->second.size())Q.push(it->second[j]);
				mp.erase(it);
			}
			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;
	vector<int> l(n),r(n);
	rep(i,n)cin>>l[i]>>r[i];
	
	long long ans = 0;
	
	{
		long long ok = -1,ng = 2000000000;
		while(ng-ok>1LL){
			
			long long mid = (ok+ng)/2;
			if(check(l,r,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(l,r,mid)<=-1)ok = mid;
			else ng =mid;
		}
		ans -= ok;
	}
	cout<<ans<<endl;
	
	
	return 0;
}