import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.StringWriter;

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */
import java.util.HashSet;
import java.util.StringTokenizer;

/**
 *
 * @author cteam66
 */
public class unique  {
    public static void main(String args[])  throws IOException {
        StringWriter sw = new StringWriter();
        BufferedReader bfr = new BufferedReader(new InputStreamReader(System.in));
        String line = bfr.readLine();
        while(!line.equals("0 0")) {
            StringTokenizer tokenizer = new StringTokenizer(line);
            int number = Integer.valueOf(tokenizer.nextToken());
            int intervals = Integer.valueOf(tokenizer.nextToken());
            int[] numbers = new int[number];
            for(int i = 0; i < number; i++) {
                numbers[i] = Integer.valueOf(bfr.readLine());
            }
            for(int i = 0; i < intervals; i++) {
                line = bfr.readLine();
                tokenizer = new StringTokenizer(line);
                int from = Integer.valueOf(tokenizer.nextToken());
                int to = Integer.valueOf(tokenizer.nextToken());
                int size = 1;
                HashSet<Integer> set = new HashSet<Integer>(number);
                for(int j = from - 1; j < to; j++) {
                    set.add(numbers[j]);
                    if(set.size() == size) {
                        size++;
                    } else {
                        sw.append(numbers[j] + "");
                        break;
                    }
                }
                if (set.size() == (to - from + 1)) {
                    sw.append("OK");
                }
                sw.append("\n");
            }
            sw.append("\n");
            bfr.readLine();
            line = bfr.readLine();
        }
        System.out.print(sw);
    }
}