#include <bits/stdc++.h>
using namespace std;
#define ll long long int
#define oo 1e15 + 9
#define pii pair<ll, ll>
int main(){
int n; cin >> n;
pii arr[n];
for (int i = 0; i < n; i++)
{
cin >> arr[i].first >> arr[i].second;
}
sort(arr, arr + n);
ll PreSum[n + 1];
PreSum[0] = 0;
for (int i = 1; i <= n; i++)
{
PreSum[i] = PreSum[i - 1] + arr[i - 1].second;
}
multiset<ll> s;
for (int i = 1; i <= n; i++)
{
s.insert(PreSum[i] - arr[i - 1].first);
}
ll ans = 0;
for (int i = 0; i < n; i++)
{
ll b = *prev(s.end());
ans = max(ans, b - PreSum[i] + arr[i].first);
s.erase(s.find(PreSum[i + 1] - arr[i].first));
}
cout << ans;
}
