#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define FOR(i, a, b) for (int i = (a); i <= (b); ++i)
template <class X, class Y>
bool maximize(X &x, Y y) {
if (x < y) return x = y, true;
else return false;
}
template <class X, class Y>
bool minimize(X &x, Y y) {
if (x > y) return x = y, true;
else return false;
}
#define sz first
#define val second
const int maxn = (int) 5e5 + 7;
pair <long long, long long> a[maxn + 2];
int main() {
ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
int n;
cin >> n;
FOR(i, 1, n) cin >> a[i].sz >> a[i].val;
sort(a + 1, a + 1 + n);
a[0].val = 0;
FOR(i, 1, n) a[i].val += a[i - 1].val;
ll pref = 0, ans = 0;
// a[j].val - a[i - 1].val - (a[j].sz - a[i].sz) is maximize;
// a[j].val - a[j].sz - (a[i - 1].val - a[i].sz);
FOR(i, 1, n) {
minimize(pref, a[i - 1].val - a[i].sz);
maximize(ans, a[i].val - a[i].sz - pref);
}
cout << ans;
return 0;
}
