#include <cstdio>

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

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

	return 0;
}