import java.io.BufferedReader;
import java.io.InputStreamReader;

public class Main {
	public static void main(String[] args) throws Exception {

		BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
		int N = Integer.parseInt(reader.readLine());
		String[] str = reader.readLine().split(" ");
		int[] n = new int[2*N];
		for (int i = 0; i < 2*N; i++) {
			n[i] = Integer.parseInt(str[i]);
		}
		int max = 0;
		for (int b = 0; b < N; b++) {   //しきり
			int keep = 0;
			for (int a = 0; a < N; a++) {  //中の数
				if (a <= b) {
					keep += n[2*a] - n[2*a+1];
				}
				else {
					keep += n[2*a+1] - n[2*a];
				}
			}
			if (max < keep) {
				max = keep;
			}
		}
		System.out.println(max);
	}
}