#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pb push_back
#define fi first
#define se second
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int n;
cin >> n;
vector<pair<ll, ll>> obrazy(n);
for (int i = 0; i < n; i++) {
cin >> obrazy[i].fi >> obrazy[i].se;
}
sort(obrazy.begin(), obrazy.end());
ll best = -1e18, s = 0, wyn = 0;
for (int i = 0; i < n; i++) {
ll wiel = obrazy[i].fi, war = obrazy[i].se;
best = max(best, wiel - s);
s += war;
wyn = max(wyn, best + s - wiel);
}
cout << wyn;
}
