#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cassert>
#include <cmath>

#include <algorithm>
#include <vector>
#include <queue>
#include <stack>
#include <deque>
#include <list>
#include <set>
#include <map>
using namespace std;

#define FOR(i,a,b) for(int i=(a); i<(b); ++i)
#define REP(i,n) for(int i=1; i<=(n); ++i)
#define pb push_back
#define INF 1000000001
#define EPS 10e-9
#define P 1000000007
typedef vector<int> vi;
typedef pair<int,int> pii;
#define st first
#define nd second
typedef long long ll;
typedef unsigned long long ull;
#define ISDEBUG 1
#define dprintf if(ISDEBUG) printf
void PTAB(const vi& t) {FOR(i,0,t.size()) printf("%d ", t[i]); puts("");}
#define DPTAB if(ISDEBUG) PTAB

vi d;

int g(int i) {
	return ((i^(i-1)) +1) /2;
}

int query(int i) {
	if(i==0) return 0;
	int result = 0;
	while(i>0) {
		result = max(result, d[i]);
		i -= g(i);
	}
	return result;
}

int update(int i, int x) {
	while(i<d.size()) {
		d[i] = max(d[i], x);
		i += g(i);
	}
}

int main() {
	int m,q;
	while(scanf("%d%d", &m, &q), m&&q) {
		map<int,int> last;
		vi res(m+1, 0);
		d.clear();
		int M=1;
		while(M<=m) M<<=1;
		d.resize(M, 0);
		REP(i,m) {
			int x; scanf("%d", &x);
			if(last.count(x)) update(i, last[x]);
			if(query(i)>query(i-1)) res[i]=x;
			else res[i] = res[i-1];
			last[x] = i;
		}
		REP(i,q) {
			int a,b; scanf("%d%d", &a, &b);
			if(query(b) >= a) printf("%d\n", res[b]);
			else puts("OK");
		}
		puts("");
	}
	return 0;
}