#include <bits/stdc++.h>
using namespace std;
#define int long long
signed main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
int n;
cin >> n;
vector<pair<int, int>> v(n);
for (int i = 0; i < n; i++) {
cin >> v[i].first >> v[i].second;
}
sort(v.begin(), v.end());
vector<int> pre(n + 1, 0);
for (int i = 0; i < n; i++) {
pre[i + 1] = pre[i] + v[i].second;
}
int ans = LLONG_MIN;
int temp = pre[0] - v[0].first;
for (int r = 1; r <= n; r++) {
ans = max(ans, pre[r] - v[r - 1].first - temp);
if (r < n) {
temp = min(temp, pre[r] - v[r].first);
}
}
cout << ans;
return 0;
}
