#include <iostream>
#include <fstream>
#include <algorithm>
using namespace std;
ifstream in ("orase.in");
ofstream out("orase.out");
struct oras{long x,y;};
int const N=50005;
oras v[N];
long n,maxi;
bool cmp(oras a, oras b)
{
    if(a.x<b.x) return true;
    return false;
}
int main()
{
    n=1;    int dc,u=1;
    while(in>>v[n].x>>v[n].y)
        n++;
    sort(v+1,v+n,cmp);
    maxi=v[1].x+v[1].y;
    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;
}