#include <bits/stdc++.h>
using namespace std;
struct timp
{
    int x,y;
}a[100004];
int n,i,j,v[100004];
int compareee(timp a,timp b)
{
    return ((a.y<b.y)||(a.y==b.y&&a.x>b.x));
}
ifstream f("heavymetal.in");
ofstream g("heavymetal.out");
int main()
{
    f>>n;
    for(i=1;i<=n;i++)
    {
        f>>a[i].x>>a[i].y;
    }

    sort(a+1,a+n+1,compareee);
    for(i=1;i<=n;i++)
    {
        cout<<a[i].x<<' '<<a[i].y<<endl;
    }
    i=1;
    for(j=1;j<=a[n].y;j++)
    {
        v[j]=v[j-1];
        while (a[i].y==j)  {v[j]=max(v[j],v[a[i].x]+a[i].y-a[i].x);
             i++;}
    }
    g<<v[a[n].y];
  return 0;
}