#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
typedef long long int ll;
int N;
vector<pair<ll, ll>> artworks;
int main() {
ios::sync_with_stdio(false);
cin.tie(NULL);
cin >> N;
artworks = vector<pair<ll, ll>>(N);
for (int i = 0; i < N; i++)
cin >> artworks[i].first >> artworks[i].second;
sort(artworks.begin(), artworks.end());
vector <ll> cum(N);
cum[0] = artworks[0].second;
for (int i = 1; i < N; i++)
cum[i] = cum[i-1] + artworks[i].second;
ll maxSum[N];
maxSum[N-1] = cum[N-1] - artworks[N-1].first;
for (int i = N-2; i >= 0; i--)
maxSum[i] = max(cum[i] - artworks[i].first, maxSum[i+1]);
ll record = max(artworks[0].second, maxSum[0] + artworks[0].first);
for (int i = 1; i < N; i++)
record = max(record, max(artworks[i].second, maxSum[i] + artworks[i].first - cum[i-1]));
cout << record << '\n';
return 0;
}
