#include <iostream>
#include <map>

using namespace std;

int main() {
	while (1) {
		int m, q, i, j;
		scanf("%d %d", &m, &q);
		
		if (m == 0 && q == 0) {
			break;
		}
		
		int ids[m];
		for (i = 0; i < m; ++i) {
			scanf("%d", ids + i);
		}
		map<int, bool> counts;
		for (i = 0; i < q; ++i) {
			int start, end;
			scanf("%d %d", &start, &end);
			for (j = start - 1; j < end; ++j) {
				bool &id = counts[ids[j]];
				if (!id) {
					id = 1;
				} else if (id) {
					printf("%d", ids[j]);
					goto nazdar;
				}
			}
			printf("OK");
		nazdar:
			putchar('\n');
			counts.clear();
		}
		putchar('\n');
	}
	return 0;
}