#include "bits/stdc++.h"
using namespace std;
#define int long long
signed main() {
int N, ans = 0;
cin >> N;
vector<int> D(N), M(N + 1);
vector<pair<int, int> > art(N);
for (int i = 0; i < N; i++) cin >> art[i].first >> art[i].second;
sort(art.begin(), art.end());
for (int i = 1; i < N; i++) M[i] = D[i] = -(art[i].first - art[i - 1].first) + art[i].second + D[i - 1];
for (int i = N - 2; i >= 0; i--) M[i] = max(M[i], M[i + 1]);
for (int i = 0; i < N; i++) ans = max(ans, max(art[i].second, art[i].second + M[i + 1] - D[i]));
cout << ans;
}
