#include "bits/stdc++.h"
using namespace std;
using i64 = long long;
using u64 = unsigned long long;
using i32 = int;
using u32 = unsigned;
using i16 = short;
using u16 = unsigned short;
using ld = long double;
using ii = pair<int, int>;
void solve() {
int n;
cin >> n;
vector<pair<i64, i64>> a(n);
vector<i64> pre(n + 1);
i64 ans, suf;
for(auto& [x, y] : a) cin >> x >> y;
sort(a.begin(), a.end());
pre[0] = 0;
for(int i = 1; i <= n; ++i) pre[i] = pre[i - 1] + a[i - 1].second;
ans = suf = LLONG_MIN;
for(int i = n - 1; i >= 0; --i) {
suf = max(suf, pre[i + 1] - a[i].first);
ans = max(ans, suf - pre[i] + a[i].first);
}
cout << ans << '\n';
}
int main() {
ios_base :: sync_with_stdio(false);
cin.tie(0);
int t = 1;
//cin >> t;
while(t--) solve();
return 0;
}
