/*
 * ACM ICPC - CERC 2011
 *
 * Sample solution: unique
 * Author: Jan Katrenic
 */

#include <cstdio>
#include <set>
#include <map>
#include <vector>
#include <algorithm>
using namespace std;

int n,m;
vector<int> value;

int main(){
for(;;) {
  scanf("%d %d\n", &n, &m);
  if (!n) return 0;
  value.resize(n);
  for (int i = 0; i < n; i++) {
    scanf("%d", &value[i]);
  }

  map<int,int> last_occ;
  vector<int> first_match(n);
  for (int i = n-1; i >= 0; i--) {
    first_match[i] = n;  
    if (i < n-1) first_match[i] = first_match[i+1];
    if (last_occ.count(value[i]))
      first_match[i] = min(first_match[i], last_occ[value[i]]);
    last_occ[value[i]] = i;
  }

  for (int i = 0; i < m; i++) {
    int x, y;
    scanf("%d %d",&x, &y); x--; y--;
    if (first_match[x] <= y) {
      printf("%d\n",value[first_match[x]]);
    } else {
      printf("OK\n");
    }
  }
  printf("\n");
}
}