#include <bits/stdc++.h>
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define vi vector <int>
#define pb push_back
using namespace std;
using i64 = long long;
using u64 = unsigned long long;
template <typename T>
using PQmin = priority_queue <T, vector <T>, greater <T>>;
int n;
i64 S, pre, ans;
int main(){
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
cin >> n;
vector <pair <i64, int>> art(n);
for(auto &x : art)
cin >> x.first >> x.second;
sort(all(art));
for(int i = 0; i < n; ++i){
auto &a = art[i];
ans = max(ans, S + a.second - a.first - pre);
pre = min(pre, S - a.first);
S += a.second;
}
cout << ans;
return 0;
}
