// I ♡ 鞠婧祎
// #pragma GCC optimize("Ofast")
// #pragma GCC target("avx,avx2,fma")
#include <bits/stdc++.h>
#define freopen(name) if(fopen(name".INP","r")) {freopen (name".INP","r",stdin); freopen (name".OUT","w",stdout);}
using namespace std;
using ll = long long;
void justDoIt();
int main() {
// freopen("");
ios_base::sync_with_stdio(false);
cin.tie(0);
justDoIt();
return 0;
}
const int N = 5e5 + 5;
ll pre[N];
pair<ll, int> a[N];
void test() {
int n;
cin >> n;
for (int i = 1; i <= n; i++) {
cin >> a[i].first >> a[i].second;
}
sort(a + 1, a + n + 1);
ll res = -1e18, t = 0;
for (int i = 1; i <= n; i++) {
pre[i] = pre[i - 1] + a[i].second;
res = max(res, pre[i] - a[i].first - t);
t = min(t, pre[i - 1] - a[i].first);
}
cout << res;
}
void justDoIt() {
int t = 1;
// cin >> t;
for (int tests = 1; tests <= t; tests++) {
test();
}
}
