#include<cstdio>
#include<map>

using namespace std;

int M,Q;
map<int,int> last;
int L[1001001];
int val[1001001];
int x[1001001];

int main()
{
	while(scanf("%d%d",&M,&Q),M+Q)
	{
		last.clear();
		for(int i=0;i<M;++i)
		{
			if (i)
			{
				L[i]=L[i-1];
				val[i]=val[i-1];
			}
			else
			{
				L[i]=0;
				val[i]=-1;
			}
			scanf("%d",x+i);
			if (last.find(x[i])!=last.end()&&last[x[i]]+1>L[i])
			{
				L[i]=last[x[i]]+1;
				val[i]=x[i];
			}
			last[x[i]]=i;
		}
		for(int i=0;i<Q;++i)
		{
			int a,b;
			scanf("%d%d",&a,&b);
			if (L[b-1]<=a-1)
				puts("OK");
			else
				printf("%d\n",val[b-1]);
		}
		puts("");
	}
	return 0;
}