import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int aSum = 0;
        int bSum = 0;
        for (int i = 0; i < n - 1; i++) {
            aSum += sc.nextInt();
            bSum += sc.nextInt();
        }
        int max = Math.max(aSum, bSum);
        int min = Math.min(aSum, bSum);
        int ans = max - (max - min) + 1;
        System.out.println(ans);
    }
}