#include <iostream>
#include <map>

using namespace std;

int main()
{
map<long long, long long> counts;
	long long number[1000000];
	int l, r;
	for(;;)
	{
		
		int nn, nr;
		scanf("%d %d", &nn, &nr);
		if (!nn && !nr)
			break;

		for (int i = 0; i < nn; i++)
			scanf("%lld", &number[i]);

		for (int i = 0; i < nr; i++)
		{
			counts.clear();
			int c = 0;
			scanf("%d %d", &l, &r);
			l--; r--;
			for (int j = l; j <= r; j++)
			{
				counts[number[j]]++;
				if (counts[number[j]] > 1)
				{
					printf("%lld\n", number[j]);
					c++;
					break;
				}
			}
			if (c == 0)
				printf("OK\n");
		}
		printf ("\n");
 	}
	return 0;
}