#include <cstdio>
#include <set>

using namespace std;

int m[1000001];
int mes, q, i;
int a, f;
bool ok;

int main() {
	set<int> volt;
	while (1){
		scanf("%d %d", &mes, &q);
		if (mes == 0) break;
		for (i = 1; i <= mes; i++)
			scanf("%d", &(m[i]));
		for (int j = 0; j < q; j++){
			scanf("%d %d", &a, &f);
			ok = true;
			volt.clear();
			for (i = a; i <= f; i++){
				if (volt.find(m[i]) != volt.end()){
					printf("%d\n", m[i]);
					ok = false;
					break;
				} else {
					volt.insert(m[i]);
				}
			}
			if (ok) printf("OK\n");
		}
		scanf("\n");
		printf("\n");
	}

	return 0;
}