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

		System.out.println(Math.max(a, b) - Math.abs(a - b) + 1);
	}
}