#include <bits/stdc++.h>
using namespace std;
void setup()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
}
int n;
long long a[500001], b[500001], c[500001], res;
pair<long long, int> p[500001];
int main()
{
setup();
cin >> n;
for (int i = 1; i <= n; ++i)
{
cin >> p[i].first >> p[i].second;
}
sort(p + 1, p + 1 + n);
for (int i = 1; i <= n; ++i)
{
a[i] = p[i].first;
b[i] = b[i - 1] + p[i].second;
c[i] = b[i] - a[i];
}
for (int i = n - 1; i >= 0; --i)
{
c[i] = max(c[i], c[i + 1]);
}
for (int i = 1; i <= n; ++i)
{
res = max(res, c[i] - b[i - 1] + a[i]);
}
cout << res;
return 0;
}
