#include "bits/stdc++.h"
using namespace std;
void solve();
bool multitest();
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
clock_t TIME = clock();
int TEST = 1;
if (multitest()) cin >> TEST;
while (TEST--) solve();
cerr << "\nUsed: " << clock() - TIME << " ms\n\n";
}
bool multitest() {
return 0;
}
const int NM = 5e5 + 5;
int n;
pair<long long, long long> a[NM];
long long p[NM];
void solve() {
cin >> n;
for (int i = 1; i <= n; ++i)
cin >> a[i].first >> a[i].second;
sort(a+1, a+n+1);
for (int i = 1; i <= n; ++i)
p[i] = p[i-1] + a[i].second;
long long min_prefix = 0, ans = LLONG_MIN;
for (int i = 1; i <= n; ++i) {
ans = max(ans, p[i] - a[i].first - min_prefix);
min_prefix = min(min_prefix, p[i-1] - a[i].first);
}
cout << ans << "\n";
}
