#include <bits/stdc++.h>
using namespace std;
#define int long long
signed main() {
ios::sync_with_stdio(0); cin.tie();
int n; cin >> n;
pair<int, int> p[n];
for (int i = 0; i < n; ++i) {
cin >> p[i].first >> p[i].second;
}
sort(p, p + n);
vector<int> d(n);
int s = 0;
for (int i = 0; i < n; ++i) {
s += p[i].second;
d[i] = s - p[i].first;
}
for (int i = n - 2; i >= 0; --i)
d[i] = max(d[i], d[i + 1]);
int ans = 0;
int pen = 0;
for (int i = 0; i < n; ++i) {
ans = max(ans, d[i] + p[i].first + pen);
pen -= p[i].second;
}
cout << ans << endl;
return 0;
}
