#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
#define int long long
int nbTableau;
vector<pair<int, int> > caraTab;
int32_t main()
{
ios::sync_with_stdio(false);
cin >> nbTableau;
for(int i = 0; i < nbTableau; i++)
{
int a, b;
cin >> a >> b;
caraTab.push_back({a, b});
}
sort(caraTab.begin(), caraTab.end());
int cur = caraTab[0].second;
int result = cur;
for(int iTab = 1; iTab < nbTableau; iTab++)
{
cur = max(cur + caraTab[iTab].second - (caraTab[iTab].first - caraTab[iTab - 1].first), caraTab[iTab].second);
result = max(result, cur);
}
cout << result << endl;
}
