#include <algorithm>
#include <iostream>
using namespace std;
#define ll long long
#define pll pair <ll, ll>
#define fi first
#define se second
const int N = 5e5 + 10;
int n;
pll a[N];
int main() {
cin.tie(0); cout.tie(0);
ios_base::sync_with_stdio(false);
cin >> n;
for (int i = 1; i <= n; ++i) {
cin >> a[i].fi >> a[i].se;
}
sort(a + 1, a + n + 1);
ll Max = -1e18, ans = -1e18;
for (int i = 1; i <= n; ++i) {
a[i].se += a[i - 1].se;
Max = max(Max, a[i].fi - a[i - 1].se);
ans = max(ans, a[i].se - a[i].fi + Max);
}
cout << ans << "\n";
return 0;
}
