#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include <ctype.h>

#include <algorithm>

#define BUFLEN 1024
#define MAX_M 1000000

class LolException {
	public:
		unsigned int number;
	
		LolException(unsigned int number) {
			this->number = number;
		//~ printf("lold: %u\n", number);
		}
};

bool lolCompare(unsigned int a, unsigned int b) {
	if (a == b)
		throw new LolException(a);
	return a < b;
}

void solve(unsigned int keys[], unsigned int b, unsigned int e) {
	unsigned int mykeys[MAX_M + 1];
	unsigned int i;
	
	memcpy(&mykeys[b], &keys[b], sizeof(unsigned int) * (e - b + 1));
	
//~ for (i = b; i <= e; i++)
	//~ printf("%u ", mykeys[i]);
//~ printf("\n");
	try {
		std::sort(&(mykeys[b]), &(mykeys[e + 1]));
	
		for (i = b; i < e; i++)
			if (mykeys[i] == mykeys[i + 1])
				throw new LolException(mykeys[i]);
		
		printf("OK\n");
	} catch (LolException *lol) {
		printf("%u\n", lol->number);
		delete lol;
	}
}

int main(int argc, char *argv[]) {
	argc = argc;
	argv = argv;
	
	unsigned int M, Q;
	char buffer[BUFLEN];
	unsigned int m, q, b, e;
	unsigned int keys[MAX_M + 1];
	
	while (true)
	{
		fgets(buffer, BUFLEN, stdin);
		sscanf(buffer, "%d %d", &M, &Q);
		
		if (M == 0 && Q == 0)
			break;
		
		for (m = 1; m <= M; m++)
		{
			fgets(buffer, BUFLEN, stdin);
			sscanf(buffer, "%u", &(keys[m]));
		}
		
		for (q = 1; q <= Q; q++)
		{
			fgets(buffer, BUFLEN, stdin);
			sscanf(buffer, "%u %u", &b, &e);
		//~ for (m = 1; m <= M; m++)
			//~ printf("%u ", keys[m]);
		//~ printf("\n");return 1;
			solve(keys, b, e);
		}
		
		fgets(buffer, BUFLEN, stdin);
		printf("\n");
	}
	
	return 0;
}