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