import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.Arrays;

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());
		int[] l = new int[n];
		int[] r = new int[n];
		for (int i = 0; i < n; i++) {
			String[] sa = br.readLine().split(" ");
			l[i] = Integer.parseInt(sa[0]);
			r[i] = Integer.parseInt(sa[1]);
		}
		br.close();

		Arrays.sort(l);
		Arrays.sort(r);
		int maxL = 0;
		int minR = 1000000007;
		for (int i = 0; i < n; i++) {
			int i1 = i + 1;
			maxL = Math.max(maxL, l[i] - i1);
			minR = Math.min(minR, r[i] - i1);
		}
		int ans = Math.max(minR - maxL + 1, 0);
		System.out.println(ans);
	}
}