#include <iostream>
#include <vector>
#include <set>
#include <map>
#include <algorithm>
#include <cmath>
#include <queue>
#include <string>
#define ff first
#define ss second
using namespace std;
typedef long long ll;
const int N = 500010;
pair<ll, ll> a[N];
int main() {
int n;
cin >> n;
for (int i = 1; i <= n; i++) {
cin >> a[i].ff >> a[i].ss;
}
sort(a + 1, a + n + 1);
for (int i = 1; i <= n; i++) {
a[i].ss += a[i - 1].ss;
}
ll mx = -1000000000000000000;
ll ans = -1000000000000000000;
for (int i = 1; i <= n; i++) {
mx = max(mx, a[i].ff - a[i - 1].ss);
ans = max(ans, a[i].ss - a[i].ff + mx);
}
cout << ans << "\n";
}
