#include <bits/stdc++.h>
using namespace std;
#define int long long
#define all(x) x.begin(), x.end()
const int inf = -2e18;
signed main(){
ios::sync_with_stdio(0);
cin.tie(nullptr); cout.tie(nullptr);
int n, ans = inf, mx = inf, sum = 0;
cin >> n;
vector<pair<int, int>> v;
for(int i = 0, a, s; i < n; ++i){
cin >> a >> s;
v.push_back({a, s});
}
sort(v.begin(), v.end());
for(int i = 0; i < n; ++i){
mx = max(mx, -sum + v[i].first);
sum += v[i].second;
ans = max(ans, sum + mx - v[i].first);
}
cout << ans << "\n";
return 0;
}
