#include <iostream>
#include <cstdio>
#include <iomanip>
#include <algorithm>
#include <cmath>
#include <cstring>
#define int long long
using namespace std;
int n,a,b,c[101000],d[101000];
signed main(){
	cin>>n;
	for (int i=1;i<=n;i++){
		cin>>a>>b;
		c[i]=max(b,a-b);
		d[i]=max(b,b-a);
	}
	sort(c+1,c+n+1);
	sort(d+1,d+n+1);
	cout<<max(c[n]+c[n-1],d[n]+d[n-1]);
	return 0;
}