#include <bits/stdc++.h>
using namespace std;
#define int long long
#define all(x) (x).begin() + 1, (x).end()
#define F first
#define S second
#define nn '\n'
#define pb push_back
signed main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
int n;
cin >> n;
vector<pair<int, int>> a(n + 1);
for (int i = 1; i <= n; i++) {
cin >> a[i].F >> a[i].S;
}
sort(all(a));
vector<int> p(n + 1, 0);
for (int i = 1; i <= n; i++) {
p[i] = p[i - 1] + a[i].S;
}
int mn = -1;
int ans = -1;
for (int r = 1; r <= n; r++) {
ans = max(ans, p[r] - a[r].F + mn);
mn = max(mn, a[r].F - p[r - 1] );
ans = max(ans, a[r].S);
}
cout << ans << nn;
}
