#include <iostream>
#include <sstream>
#include <cstdio>
#include <cmath>
#include <cstring>
#include <cctype>
#include <string>
#include <vector>
#include <list>
#include <set>
#include <map>
#include <queue>
#include <stack>
#include <algorithm>
using namespace std;

#define DEBUG(x) cout << '>' << #x << ':' << x << endl;
#define FOR(i, a, b) for (int i = (a); i < (b); ++i)
#define FOR2(i, a, b) for (int i = (a); i > (b); --i)
inline bool EQ(double a, double b) { return fabs(a-b) < 1e-9; }

const int INF = 1<<29;
typedef long long ll;

const int MAX = 1000007;
int in[MAX];
int bp[MAX], b[MAX];

int main() {
	while(true)
	{
		int M, Q;
		scanf("%d%d", &M, &Q);
		if (!M && !Q) break;
		
		FOR(i, 0, M) scanf("%d", &in[i]);
		map<int, int> last;
		int best_pos = -1, best = -1;
		
		FOR(i, 0, M)
		{
			map<int, int>::iterator iter = last.find(in[i]);
			
			if (iter != last.end() && iter->second > best_pos)
			{
				best_pos = iter->second;
				best = iter->first;
			}
			bp[i] = best_pos;
			b[i] = best;
			
			last[in[i]] = i;
		}
		
		int be, en;
		FOR(i, 0, Q)
		{
			scanf("%d%d", &be, &en);
			--be, --en;
			if (bp[en] < be) printf("OK\n");
			else printf("%d\n", b[en]);
		}
		printf("\n");
	}
	return 0;
}