/*
Zadanie: Art Exhibition
Autor: Tomasz Kwiatkowski
*/
#include <bits/stdc++.h>
#define fi first
#define se second
#define pb push_back
using namespace std;
typedef long long ll;
const int MAXN = 1e6 + 7;
const int INF = 1e9 + 7;
int main()
{
ios_base::sync_with_stdio(0), cin.tie(0);
int n;
cin >> n;
vector<pair<ll, ll>> artworks(n);
for (auto& [a, b] : artworks)
cin >> a >> b;
sort(artworks.begin(), artworks.end());
ll maxx = -1e18;
ll ans = 0;
ll pref = 0;
for (auto [a, b] : artworks) {
maxx = max(a - pref, maxx);
pref += b;
ans = max(maxx + pref - a, ans);
}
cout << ans << '\n';
return 0;
}
