#include <bits/stdc++.h>
#define maxn 500005
#define fi first
#define se second
using namespace std;
int n;
pair<int64_t, int> a[maxn];
int64_t s[maxn];
int main() {
ios::sync_with_stdio(false);
cin.tie(NULL);
cin >> n;
for (int i = 1; i <= n; i++) cin >> a[i].fi >> a[i].se;
sort(a + 1, a + n + 1);
for (int i = 1; i <= n; i++) s[i] = s[i-1] + a[i].se;
int64_t minn = 0;
int64_t maxx = LLONG_MIN;
for (int i = 1; i <= n; i++) {
minn = min(minn, s[i-1] - a[i].fi);
maxx = max(maxx, s[i] - minn - a[i].fi);
}
cout << maxx;
}
