#include <algorithm>
#include <cstdio>
#include <map>
#include <vector>
using namespace std;
int main() {
	int m, q, b, e, M[1000001], P[1000001];
	bool first = true;
	while (true) {
		scanf("%d %d", &m, &q);
		if (m == 0 && q == 0) break;
		if (!first) puts("");
		else first = false;
		map<int, int> prev;
		map<int, int>::iterator it;
		for (int i = 1; i <= m; i++) {
			scanf("%d", M + i);
		}
		for (int i = m; i >= 1; i--) {
			it = prev.find(M[i]);
			if (it == prev.end()) {
				P[i] = 0;
				prev[M[i]] = i;
			} else {
				P[i] = it->second;
				it->second = i;
			}
		}
		#if 0
		for (int i = 1; i <= m; i++) {
			printf("%d next %d\n", M[i], P[i]);
		}
		#endif
		for (int i = 0; i < q; i++) {
			scanf("%d %d", &b, &e);
			int bad = 0;
			for (int i = b; i <= e; i++) {
				if (P[i] == 0) continue;
				if (P[i] <= e) {
					bad = M[i];
					break;
				}
			}
			if (bad == 0) puts("OK");
			else printf("%d\n", bad);
		}
	}
	return 0;
}