#include <bits/stdc++.h>
using namespace std;
pair <int64_t , int> sir[500002];
int main ()
{
ios :: sync_with_stdio(false);
cin.tie(NULL); cout.tie(NULL);
int lungime;
cin >> lungime;
for (int indice = 1 ; indice <= lungime ; indice++)
{ cin >> sir[indice].first >> sir[indice].second; }
sort(sir + 1 , sir + lungime + 1);
int64_t minim = -sir[1].first , suma = 0 , maxim = INT64_MIN;
for (int dreapta = 1 ; dreapta <= lungime ; dreapta++)
{
suma += sir[dreapta].second;
maxim = max(maxim , suma - sir[dreapta].first - minim);
minim = min(minim , suma - sir[dreapta + 1].first);
}
cout << maxim;
return 0;
}
