#include <stdio.h>
#include <stdlib.h>
#include <set>
#include <algorithm>

#define MAXN 2000000

typedef struct SETITEM
{
	int id;
	int last;
	
	SETITEM() {}
	SETITEM(int a, int b): id(a), last(b) {}
	
	int operator < (const SETITEM& Item) const {return this->id < Item.id;}
}
SETITEM;

int M[MAXN];
int B[MAXN];
int E[MAXN];

int IB[MAXN];
int IE[MAXN];
int IN[MAXN];
int nI;

int Search(int* a, int n, int k)
{
	int best = -1, besti = -1, b1 = 0, b2, b3 = n;
	while(b1 < b3)
	{
		b2 = (b1 + b3) / 2;
		if(a[b2] == k)
		{
			return b2;
		}
		else if(a[b2] > k)
		{
			b3 = b2;
		}
		else
		{
			if(a[b2] > best)
			{
				besti = b2;
				best = a[b2];
			}
			
			b1 = b2 + 1;
		}
	}
	
	return besti;
}

int main()
{
	while(1)
	{
		int m, q;
		scanf("%d%d", &m, &q);
		
		if(!(m))
		{
			break;
		}
		
		for(int i = 0; i < m; i++)
		{
			scanf("%d", M + i);
		}
		
		for(int i = 0; i < q; i++)
		{
			scanf("%d%d", B + i, E + i);
			B[i]--;
			E[i]--;
		}
		
		nI = 0;
		std::set<SETITEM> Set;
		for(int i = 0; i < m; i++)
		{
			std::set<SETITEM>::iterator it = Set.find(SETITEM(M[i], 0));
			if(it == Set.end())
			{
				Set.insert(SETITEM(M[i], i));
			}
			else
			{
				if((!(nI)) || (IB[nI - 1] < it->last))
				{
					IB[nI] = it->last;
					IE[nI] = i;
					IN[nI] = M[i];
					nI++;
				}
				
				*((int*) (&(it->last))) = i;
			}
		}
		
		/*printf("nI: %d\n", nI);
		for(int i = 0; i < nI; i++)
		{
			printf("%d -> %d\n", IB[i], IE[i]);
		}*/
		
		for(int i = 0; i < q; i++)
		{
			int b = Search(IE, nI, E[i]);
			
			if((b == -1) || (IB[b] < B[i]))
			{
				printf("OK\n");
			}
			else
			{
				printf("%d\n", IN[b]);
			}
		}
		
		printf("\n");
	}
	
	return 0;
}