#include <iostream>
#include <fstream>
using namespace std;
ifstream in ("orase.in");
ofstream out("orase.out");
struct oras{int x,y;};
int const N=50005;
oras v[N];
int n,maxi;
int main()
{
    n=1;    int dc,u=1; oras aux;
    while(in>>v[n].x>>v[n].y)
        n++;
    for(int i=1;i<n;i++)
        for(int j=i+1;j<n;j++)
            if(v[i].x>v[j].x)
            {
                aux=v[i];
                v[i]=v[j];
                v[j]=aux;
            }
    for(int i=2;i<n;i++)
    {
        dc=v[i].x-v[u].x+v[i].y+v[u].y;
        if(dc>maxi) maxi=dc;
        if(v[i].y>v[u].y+v[i].x-v[u].x)
            u=i;
    }
    out<<maxi<<"\n";
    return 0;
}