#include<bits/stdc++.h>
using namespace std;
const int N = 1e5 + 5;
vector<pair<int, int>> a(N);
vector<int> ok(N);
int INF = 1e9;
int main(){
int n; cin >> n;
for(int i = 1; i <= n; i++) cin >> a[i].first >> a[i].second;
sort(a.begin() + 1, a.begin() + n + 1);
ok[1] = a[1].second;
for(int i = 2; i <= n; i++){
ok[i] = ok[i - 1] + a[i].second;
}
// ok[r] - ok[l - 1] - a[r].first + a[l].first
int res = -INF; int maxping = -INF;
for(int i = 1; i <= n; i++){
res = max(res, a[i].first - ok[i - 1]);
maxping = max(maxping, res - a[i].first + ok[i]);
}
cout << maxping;
}
