import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Scanner;

/**
 *
 * @author muran4
 */
public class Amusement {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) throws IOException {
        // TODO code application logic here
        
        BufferedReader input = new BufferedReader(new InputStreamReader(System.in));
        
        String line;
        String[] arr;
        long[] serie;
        int num;
        while((line = input.readLine())!=null){
            num = Integer.parseInt(line);
            line = input.readLine();
            //arr = line.split(" ");
            Scanner in = new Scanner(line);
            serie = new long[num];
            for (int i = 0; i < num; i++) {
                serie[i] = in.nextLong();
            }
            if(num == 1){
                System.out.println("1");
            }else{
                long diff = serie[num-1]-serie[num-2];
                long next = serie[num-1]-diff;
                int c = num-2;
                while(c>=0&&serie[c]==next){
                    c--;
                    next = next-diff;
                }
                System.out.println(c+1+1);
            }
            
        }
    }
    
}