#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <map>

using namespace std;

int main (int argc, char ** argv) {
	int m = 0;
	int q = 0;
	scanf ("%d %d\n", &m, &q);
	while (m || q) {
		long* keys = (long*) malloc(m * sizeof(long));
		int i;
		for (i = 0; i < m; i++) {
			scanf ("%ld\n", &keys[i]);
		}

		for (i = 0; i < q; i++) {
			int low = 0;
			int high = 0;
			scanf ("%d %d\n", &low, &high);
			low--;
			map<long, int> counts;
			int j;
			for (j = 0; j < m; j++) {
				counts[keys[j]] = 0;
			}
			for (j = low; j < high; j++) {
				counts[keys[j]]++;
			}
			char output[255] = ""; 
			//ostringstream strr;
			map<long, int>::iterator it;
			for (it = counts.begin(); it != counts.end(); it++) {
				if (it->second > 1 && output[0] == '\0') {
					sprintf(output, "%ld", it->first);
				}
			}
			//output = strr.str();
			if (output[0] == '\0')
				strcpy(output, "OK");
			printf("%s\n", output);
		}
		putchar('\n');
		scanf ("%d %d\n", &m, &q);
	}

	return 0;
}