import java.io.*;
import java.util.*;
public class art {
public static void main(String[] args) throws IOException {
BufferedReader r = new BufferedReader(new InputStreamReader(System.in));
long n = Long.parseLong(r.readLine());
List<Artwork> a = new ArrayList<>();
for (long i = 0; i < n; i++) {
StringTokenizer st = new StringTokenizer(r.readLine());
long x = Long.parseLong(st.nextToken());
long y = Long.parseLong(st.nextToken());
a.add(new Artwork(x, y));
}
// sort based off of size of the artworks
a.sort(Comparator.comparingLong(artwork -> artwork.size));
// prefix sum list
List<Long> p = new ArrayList<>(Collections.nCopies((int) n, 0L));
p.set(0, a.get(0).value);
for (int i = 1; i < n; i++) {
// update the prefix sum
p.set(i, p.get(i - 1) + a.get(i).value);
}
long cur;
long res = 0;
// holds differences between prefix sums
TreeSet<Long> m = new TreeSet<>();
for (int i = (int) n - 1; i >= 0; i--) {
// sum of all up to i - current size
// i is the largest (A.max)
m.add(p.get(i) - a.get(i).size);
// get the maximum difference so far
cur = m.last() - (i > 0 ? p.get(i - 1) : 0);
// finish the expression
cur += a.get(i).size;
// are we larger?
res = Math.max(res, cur);
}
System.out.println(res);
}
static class Artwork {
long size, value;
Artwork(long size, long value) {
this.size = size;
this.value = value;
}
}
}
