#include <cstdio>
#include <cstdlib>


struct Pole{
int val;
int pos;
};

struct Rozsah{
int start;
int end;
int val;
};

int cmp(const void * a, const void * b){
    if( (*(Pole*)a).val < (*(Pole*)b).val) return -1;
    if( (*(Pole*)a).val > (*(Pole*)b).val) return 1;
    
    if( (*(Pole*)a).pos < (*(Pole*)b).pos) return -1;
    if( (*(Pole*)a).pos > (*(Pole*)b).pos) return 1;
    return 0;    
}

int bs(Rozsah * pole, int len, int x){
    bool found = false;
    int L = 1, R = len-1, mid;
    while(L<=R && !found){
	mid = (L+R)/2;
	if(pole[mid].start == x) found = true;
	else{
	    if(pole[mid].start < x) L = mid+1;
	    else R = mid-1;
	}
    }
    //printf("nalezeno: %d\n",pole[mid].start);
    if(found) return mid;
    else return mid+1;
}

int main () {

    Pole * pole;
    Rozsah * roz;
    int M, Q, j;
    int min, max, ps;
//Rozsah p[5];
//for(int i=1;i<6;i++) p[i].start = i*2;
//printf("pos: %d\n",bs(p,6,5));
//printf("pos: %d\n",bs(p,6,11));

    while(scanf("%d%d",&M,&Q), M!=0){
	M++;
	j = 1;
	pole = new Pole [M];
	roz = new Rozsah [M/2+1];
	roz[0].end = 0;
	for(int i=1;i<M;i++){
	    scanf("%d",&pole[i].val);
	    pole[i].pos = i;
	}
	qsort((void *) pole, M, sizeof(Pole), cmp);
	for(int i=2;i<M;i++){
	    if(pole[i].val == pole[i-1].val){
		if(roz[j-1].end >= pole[i].pos){
		    roz[j-1].end = pole[i].pos;
		    roz[j-1].start = pole[i-1].pos;
		    roz[j-1].val = pole[i].val;
		}else{
		    roz[j].start = pole[i-1].pos;
		    roz[j].end = pole[i].pos;
		    roz[j].val = pole[i].val;
		    j++;
		}
	    }
	}
	for(int i=0;i<Q;i++){
	    scanf("%d%d",&min,&max);
	    ps = bs(roz,j,min);
	    if(ps >= j) printf("OK\n");
	    else{
		if(max >= roz[ps].end) printf("%d\n",roz[ps].val);
		else printf("OK\n");
	    }
	}
printf("\n");
	
    }

   return 0;
}