#include<bits/stdc++.h>
using namespace std;
using ll = long long;
const int N = 1e6 + 66;
// a[i]<a[i+1]
// max(p[i] - p[j - 1] - (a[i] - a[j]))
// max(p[i] - p[j - 1] - a[i] + a[j])
// max(-a[i] + p[i] + a[j] - p[j - 1])
using pll = pair<ll,ll>;
pll a[N];
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0), cout.tie(0);
int n;
cin >> n;
for (int i = 1 ; i <= n ; ++ i) {
cin >> a[i].first >> a[i].second;
}
sort(a + 1, a + 1 + n);
ll pref = 0;
ll mx = -(ll(1e18));
ll Ans = -(ll(1e18));
for (int i = 1 ; i <= n ; ++ i) {
mx = max(mx, a[i].first - pref);
pref += a[i].second;
Ans = max(Ans, -a[i].first + pref + mx);
}
cout << Ans;
}
