import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.Scanner;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 *
 * @author silviase
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        Scanner in = new Scanner(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        tenhomu solver = new tenhomu();
        solver.solve(1, in, out);
        out.close();
    }

    static class tenhomu {
        public void solve(int testNumber, Scanner in, PrintWriter out) {
            int n = in.nextInt();
            long[] accEven = new long[n + 1];
            long[] accOdd = new long[n + 1];
            long max = -1;
            long cmp = 0;
            for (int i = 1; i <= n; i++) {
                accEven[i] = in.nextInt();
                accOdd[i] = in.nextInt();
                cmp += accOdd[i] - accEven[i];
            }

            for (int i = 0; i <= n; i++) {
                max = Math.max(max, cmp = cmp + (accEven[i] - accOdd[i]) * 2);
            }
            out.println(max);
        }

    }
}