import java.util.Arrays;
import java.util.List;
import java.util.Scanner;

public class Orbits {
    public static void main(String[] args){
        Scanner scanner = new Scanner(System.in);
        while(true){
            int input = Integer.parseInt(scanner.nextLine().trim());
            if(input == 0)
                break;
            int[] elements = new int[input];
            String[] elementsAsStrings = scanner.nextLine().trim().split(" ");
            if(elementsAsStrings.length != input) { //New-line-separated
                elements[0] = Integer.parseInt(elementsAsStrings[0]);
                for(int i=1; i<input;i++){
                    elements[i] = Integer.parseInt(scanner.nextLine());
                }
            } else {
                elements = Arrays.stream(elementsAsStrings).mapToInt(Integer::parseInt).toArray();
            }
            if(input == 1)
            {
                System.out.println(0);
                continue;
            }
            int n=1;
            while(elements[0]!= elements[n]){
                n++;
                if(n==input)
                {
                    n = 0;
                    break;
                }
            }
            for(int i=0;i<elements.length;i++){
                if(i+n == elements.length || n == 0){
                    break;
                }
                if(elements[i]!=elements[i+n]){
                    n = 0;
                    break;
                }
            }
            System.out.println(n);
        }
    }
}