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

public class Main {
	public static void main(String[] args) throws Exception {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		int n = Integer.parseInt(br.readLine());
		String[] sa = br.readLine().split(" ");
		long[] l = new long[n + 1];
		long[] r = new long[n + 1];
		for (int i = 0; i < n; i++) {
			l[i + 1] = Integer.parseInt(sa[i * 2]);
			r[i + 1] = Integer.parseInt(sa[i * 2 + 1]);
		}
		br.close();

		for (int i = 1; i <= n; i++) {
			l[i] += l[i - 1];
			r[i] += r[i - 1];
		}
		long total = l[n] + r[n];

		long ans = Long.MIN_VALUE;
		for (int i = 0; i <= n; i++) {
			long val1 = l[i] + r[n] - r[i];
			long val2 = total - val1;
			val1 -= val2;
			ans = Math.max(ans, val1);
		}
		System.out.println(ans);
	}
}