#include <bits/stdc++.h>
#define int long long
#define float long double
#define pii pair<int, int>
#define tii tuple<int, int, int>
#define f first
#define s second
#define ve vector
#define emb emplace_back
#define em emplace
using namespace std;
const int inf = 1e18;
const int mod = 1e9 + 7;
int32_t main() {
ios_base::sync_with_stdio(0); cin.tie(0);
int n;
cin >> n;
ve<pii> a(n);
for (auto &[x, y] : a) cin >> x >> y;
sort(a.begin(), a.end());
ve<int> pfx(n+1);
for (int i = 1; i <= n; i++) pfx[i] = pfx[i-1] + a[i-1].s;
int ans = -inf, mx = -inf;
for (int i = n; i >= 1; i--) {
mx = max(mx, pfx[i] - a[i-1].f);
ans = max(ans, a[i-1].f - pfx[i-1] + mx);
}
cout << ans;
}
