#include <bits/stdc++.h>
using namespace std;
#define ll long long
const int nx = 5e5 + 5;
int n;
ll a[nx], qs[nx];
ll dp[nx];
int main() {
ios_base::sync_with_stdio(0), cin.tie(0);
cin >> n;
vector<pair<ll,ll>> v;
for (int i = 1; i <= n; i++) cin >> a[i] >> qs[i], v.emplace_back(a[i], qs[i]);
sort(v.begin(), v.end());
for (int i = 1; i <= n; i++) {
a[i] = v[i - 1].first;
qs[i] = v[i - 1].second;
qs[i] += qs[i - 1];
}
ll ans = -1e18;
fill(dp, dp + n + 1, -1e18);
for (int i = 1; i <= n; i++) {
dp[i] = max(dp[i - 1], a[i] - qs[i - 1]);
ans = max(ans, -a[i] + qs[i] + dp[i]);
//cout << -a[i] + qs[i] + dp[i] << " " << a[i] - qs[i - 1] << endl;
}
cout << ans;
}
/*
6
4 1
1 5
10 3
9 1
4 2
5 3
7
3
2 3
11 2
4 5
6
*/
