#include <fstream>
#include <algorithm>
#define nMax 201
using namespace std;
ifstream fin("wanted.in");
ofstream fout("wanted.out");
int i, n, Max;
struct Streets
{
    int x;
    int y;
}v[nMax];
int cmp(Streets o, Streets p)
{
    return o.x<p.x;
}
void Binara(int st, int dr, int poz, int dist)
{
    if(st<=dr)
    {
        int mijl=st+(dr-st)/2;
        if(poz>v[mijl].x)
            dist+=(poz-v[mijl].x);
        else
            dist+=(v[mijl].x-poz);
        dist+=v[mijl].y;
        if(st<dr)
            dist+=v[mijl].y;
        if(st<=dr)
        {
            Binara(st, mijl-1, v[mijl].x, dist);
            Binara(mijl+1, dr, v[mijl].x, dist);
        }
        Max=max(Max, dist);
    }
}
int main()
{
    fin>>n;
    for(i=1;i<=n;i++)
        fin>>v[i].x>>v[i].y;
    sort(v+1, v+n+1, cmp);
    Binara(1, n, 0, 0);
    fout<<Max;
    return 0;
}