#include <iostream>
#include <fstream>
using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");
struct segment
{
    int capat;
    int lungime;
    int a;
};
segment x[100],aux;

int main()
{
    int n,k,i,l=1,b,j,s=0,maxx,a,m,nr,y[100],ok,poz;
    f>>n;
    s=0;
    maxx=1;
    for(i=1; i<=n; i++)
    {
        f>>x[i].capat;
        f>>x[i].lungime;

    }
    ok=0;
    while(ok==0)
    {
        ok=1;
        for(i=1; i<n; i++)
            if(x[i].capat>x[i+1].capat)
            {
                aux=x[i];
                x[i]=x[i+1];
                x[i+1]=aux;
                ok=0;
            }
    }
    a=x[i].lungime+x[i].capat;
    for(i=1; i<n; i++)
    {
        if(x[i+1].capat<=a)
        {
            a=x[i].capat+(x[i+1].lungime-x[i].capat);
            poz=i;
        }
        if(a<=x[i+1].capat)
        {
            a=(x[i+1].capat-a)+(x[i+1].lungime+x[i+1].capat);
            poz=i;
        }
        if(a>=x[i+1].lungime)
            i++;
    }

    g<<a+x[1].capat+x[1].lungime;
    return 0;
}