//team42 (Lukasz Zatorski, Damian Rusak, Krzysztof Piecuch)
#include <cstdlib>
#include <cstdio>
#include <iostream>
#include <vector>
#include <set>
#include <queue>
#include <algorithm>
#include <string>
#include <cstring>
#include <cmath>
#include <ctime>
#include <cassert>
using namespace std;

typedef long long int ll;
typedef pair<int,int> pi;
typedef vector<int> vi;
typedef vector< vi > vii;

#define ft first
#define sd second
#define mp make_pair
#define pb push_back
#define REP(i,a,b) for(register int i = a ; i < b; i++)
#define DOWN(i,a,b) for(register int i = a; i>=b ; i--)
#define WSK(C) typeof((C).begin())
#define FOREACH(wsk, C) for(WSK(C) wsk = (C).begin(); wsk!=(C).end; wsk++)

int n,m,a,b,c,q,w,r,x,t,y;
int A[1000100];
set<pair<int,int> >S;
set<pair<int,int> >::iterator it,it2;
vector<pair<pair<int,int>, int> >V;
pair<int,int>E[1000100];
int Okej[1000100];

int main(){
int uu=0;
while(1){
	uu++;
	scanf("%d%d", &m, &q);
	if(m==0 && q==0){
			return 0;
	}
	REP(i,0,m) scanf("%d", &A[i]);
	REP(i,0,q) Okej[i] = -1;
	S.clear();
	V.clear();
	REP(i,0,m){
		a = A[i];
		it = S.lower_bound(mp(a,-1));
		if(it==S.end() || (*it).ft != a) {
			S.insert(mp(a,i));
		}
		else{
			b = (*it).second;
			S.erase(it);
			S.insert(mp(a,i));
			V.pb(mp(mp(i,b), -a-1));
		}
	}
	
	REP(i,0,q){
		scanf("%d%d", &a,&b);
		a--;b--;
		E[i] = mp(a,b);
		V.pb(mp(mp(a,-1), i));
		V.pb(mp(mp(b,2000000),i));
	}
	S.clear();
	
	sort(V.begin(), V.end());
	
	bool czy = 0;
	int n = V.size();
	REP(i,0,n){
		a = V[i].ft.ft;
		b = V[i].ft.sd;
		c = V[i].sd;
		if(b == -1){
			S.insert(mp(a,c));
		}
		else if(c >= 0){
			x = E[c].ft;
			it = S.find(mp(x,c));
			if(it!=S.end())
			S.erase(it);
		}
		else{
		it = S.begin();
			while(it!=S.end()){
				it++;
			}
		
			it = S.upper_bound(mp(b+1,-1));
			if(it==S.begin()) { continue;}
			it--;
			
			czy = false;
			c = -c-1;
			do{
				
		//		cout << " c= " << c << endl;
				x = (*it).sd;
				Okej[x] = c;
				it2 = it;
				it--;
				if(it2==S.begin()) czy = true;
				S.erase(it2);
				
			}while(!czy);
		}
	}
	
	REP(i,0,q){
		if(Okej[i] == -1) printf("OK\n");
		else printf("%d\n", Okej[i]);
	}
	printf("\n");
	
}
	return 0;
}