#include <fstream>

#include <iostream>

using namespace std;

ifstream in("heavymetal.in");
ofstream out("heavymetal.out");

int pair1[100001], pair2[100001], s[100001],maxi=-1,n;

void rez(int poz, int sum)
{
    for(int i=poz+1; i<=n; i++)
    {
        if(sum+pair2[i]-pair1[i] > maxi)
            maxi=sum+pair2[i]-pair1[i];
        rez(i,sum+pair2[i]-pair1[i]);
    }
}

int main()
{
    int i, j, suma=0;
    in >> n;
    for (i = 1; i <= n; i++)
        in >> pair1[i] >> pair2[i];
    for (i = 1; i <= n; i++)
        for (j = i + 1; j <= n; j++)
            if (pair1[i] > pair1[j])
            {
                swap(pair1[i], pair1[j]);
                swap(pair2[i], pair2[j]);
            }
            else if (pair1[i] == pair1[j] && pair2[i] > pair2[j])
            {
                swap(pair1[i], pair1[j]);
                swap(pair2[i], pair2[j]);
            }
        rez(1,0);
    //for (i = 1; i <= n; i++)
        //cout << pair1[i] << " " << pair2[i] << endl;
    out << endl  << maxi;
}