#include <bits/stdc++.h>
#include <cstdio>
#define int long long
using namespace std;
void solve() {
int n;
cin >> n;
vector <pair <int, int>> val(n);
for (auto &[a, b] : val) {
cin >> a >> b;
}
sort(val.begin(), val.end());
vector <int> prev(n + 1, 0);
for (int i = 0; i < n; ++i) {
prev[i + 1] = prev[i] + val[i].second;
}
int mn = 2e16;;
int ans = 0;
for (int i = 0; i <= n; ++i) {
// cout << prev[i] << " " << mn << '\n';
ans = max(ans, prev[i] - mn - (i == 0 ? 0 : val[i - 1].first));
mn = min(mn, prev[i] - val[i].first);
}
cout << ans << '\n';
}
signed main() {
cin.tie(0);
ios::sync_with_stdio(false);
int t = 1;
// cin >> t;
for (int i = 0; i < t; ++i) {
solve();
}
}
