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  {
    
    private static class node
    {
        public int vrchol;
        public node mensi;
        public node vetsi;
        
        public node(int key)
        {
            this.vrchol = key;
        }
    }
    
    
    public static node Vrchol;
    
    public static boolean add(int key)
    {
        node tmp = Vrchol;
        node parent = null;
        
        if(tmp == null)
        {
            Vrchol = new node(key);
            return true;
        }
                
        while(tmp !=null)
        {
            if(tmp.vrchol == key)
            {
                return false;
            } else if( key > tmp.vrchol) {
                parent = tmp;
                tmp = tmp.vetsi;
            } else {
                parent = tmp;
                tmp = tmp.mensi;
            }
        }
        
        tmp = new node(key);
        if(key > parent.vrchol)
        {
            parent.vetsi = tmp;
        } else {
            parent.mensi = tmp;
        }
       return true; 
    }
    
    public static void main(String args[])  throws IOException {
        StringWriter sw = new StringWriter();
        BufferedReader bfr = new BufferedReader(new InputStreamReader(System.in));
        //Scanner sc = new Scanner(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;
                Vrchol = null;
                boolean event = false;
                //HashSet<String> set = new HashSet<String>(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(!add(numbers[j]))
                    {
                        sw.append(numbers[j]+"");
                        event = true;
                        break;
                    }
                }
                if (!event) {
                    sw.append("OK");
                }
                sw.append("\n");
            }
            sw.append("\n");
            bfr.readLine();
            line = bfr.readLine();
        }
        System.out.print(sw);
    }
}