#include <bits/stdc++.h>
typedef long long ll;
using namespace std;
int main() {
ll n; cin >> n;
vector<pair<ll, ll>> art(n);
vector<ll> prefix(n);
for (int i = 0; i < n; i++) {
cin >> art[i].first >> art[i].second;
}
sort(art.begin(),art.end());
prefix[0] = art[0].second;
for(int i = 1; i < n; i++) prefix[i] = prefix[i-1] + art[i].second;
ll fm = 0, mx = -1e18, total = 0, idx = 0;
for (int i = 0; i < n; i++) {
total += art[i].second;
if (total - art[i].first >= mx) {
mx = total - art[i].first;
fm = art[i].first;
idx = i;
}
}
ll mini = -1e18;
total = 0;
for (int i = idx; i >= 0; i--) {
if(i - 1 >= 0) total = prefix[idx] - prefix[i-1];
else total = prefix[idx];
if (total - fm + art[i].first >= mini) mini = total - fm + art[i].first;
}
ll trial2 = -1e18, sm = 0, idx2 = 0;
total = 0;
for(int i = 0; i < n; i++) {
if(i - 1 >= 0) total = prefix[n-1] - prefix[i-1];
else total = prefix[n-1];
if(total + art[i].first > trial2) {
trial2 = total - art[i].first;
sm = art[i].first;
idx2 = i;
}
}
total = 0;
ll ans2 = -1e18;
for (int i = idx2; i < n; i++) {
if(idx2 - 1 >= 0) total = prefix[i] - prefix[idx2-1];
else total = prefix[i];
if (total - art[i].first + sm >= ans2) ans2 = total - art[i].first + sm;
}
total = 0;
ll ans3 = -1e18;
for (int i = 0; i < n; i++) {
if(i - 1 >= 0) total = prefix[n-1] - prefix[i-1];
else total = prefix[n-1];
if (total - art[n-1].first + art[i].first >= ans3) ans3 = total - art[n-1].first + art[i].first;
}
for (int i = 0; i < n; i++) if(art[i].second > mini) mini = art[i].second;
cout << max({mini, ans2, ans3});
return 0;
}
