#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const int N = 5e5 + 5;
vector<pair<ll, ll>> a(N);
vector<ll> ok(N, 0);
ll INF = 1e18;
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;
}
ll res = -INF; ll 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;
}
