#include <cstdio>
#include <cmath>
#include <cstring>
#include <cctype>
#include <cstdlib>
#include <climits>
#include <vector>
#include <stack>
#include <queue>
#include <map>
#include <set>
#include <list>
#include <algorithm>
#include <string>

#define FOR(i,m,n) for (int i = m; i < n; i++)

using namespace std;

struct Bod {
  int x;
  int typ;
  int y;
  bool operator<(const Bod &b) const {
    return (x<b.x || (x==b.x && typ>b.typ));
  }
};

int M, Q;
vector<Bod> body;
vector<int> seq2;
vector<int> seq;
vector<int> sorted;
vector<pair<int,int> > interval;
vector<pair<int,int> > sint;
int posl[1200000];
int vysl[1200000];
int aktivni[1200000];

bool porovnej_pair(const pair<int,int> &a, const pair<int,int> &b) {
  return (a.first<b.first || (a.first==b.first && a.second<b.second));
}

bool solve() {
  seq.clear(); sorted.clear(); interval.clear(); sint.clear(); seq2.clear(); body.clear();
  scanf("%d%d", &M, &Q);
  FOR (i, 0, M) posl[i] = -1;
  FOR (i, 0, Q) { vysl[i] = -1; aktivni[i] = true; }
  if (M==0 && Q==0) return false;
  
  FOR (i, 0, M) {
    int x; scanf("%d", &x);
    seq2.push_back(x);
    sorted.push_back(x);
  }
  sort(sorted.begin(), sorted.end());
  // precislovani
  FOR (i, 0, seq2.size()) {
    int q = lower_bound(sorted.begin(), sorted.end(), seq2[i]) - sorted.begin();
    seq.push_back(q);
  }
  FOR (i, 0, seq.size()) {
    if (posl[seq[i]]!=-1) {
      Bod a; a.x = posl[seq[i]]; a.typ = 1;
      Bod b; b.x = i; b.typ = 2;
      a.y = b.x; b.y = a.x;
      body.push_back(a); body.push_back(b);
    }
    posl[seq[i]] = i;
  }
  FOR (i, 0, Q) {
    int a, b;
    scanf("%d%d", &a, &b);
    a--;
    b--;
    interval.push_back(pair<int,int>(a, b));
    sint.push_back(pair<int,int>(a, b));
    Bod A; A.x = a; A.typ = 3;
    Bod B; B.x = b; B.typ = 4;
    A.y = B.x; B.y = A.x;
    body.push_back(A); body.push_back(B);
  }
  sort(sint.begin(), sint.end(), porovnej_pair);
  sort(body.begin(), body.end());
  //FOR (i, 0, body.size()) printf("%d (%d) - %d\n", body[i].x, body[i].y, body[i].typ);
  // Sweep line
  vector<Bod> heap; int K = 0;
  FOR (i, 0, body.size()) {
    switch(body[i].typ) {
      case 1:
        //printf("1\n");
        while (heap.size()>0 && heap[0].x >= body[i].y) {
          int a = heap[0].y;
          int b = heap[0].x;
          int index = lower_bound(sint.begin(), sint.end(), pair<int,int>(a,b), porovnej_pair) - sint.begin();
          //printf("index %d\n", index);
          if (aktivni[index]) {
            //printf("interval %d,%d je spatny, protoze %d,%d\n", a, b, body[i].x, body[i].y);
            // vysledek pro tento interval
            //printf("x %d\n", body[i].x);
            vysl[index] = seq2[body[i].x];
            aktivni[index] = false;
          }
          pop_heap(heap.begin(), heap.end());
          heap.pop_back(); K--;
        }
        break;
      case 2:
        //printf("2\n");
        break;
      case 3:
        //printf("3\n");
        heap.push_back((Bod){body[i].y, 4, body[i].x});
        push_heap(heap.begin(), heap.end()); K++;
        break;
      case 4:
        //printf("4\n");
        int a = body[i].y;
        int b = body[i].x;
        int index = lower_bound(sint.begin(), sint.end(), pair<int,int>(a,b), porovnej_pair) - sint.begin();
        aktivni[index] = false;
        break;
    }
  }
  
  FOR (i, 0, interval.size()) {
    int index = lower_bound(sint.begin(), sint.end(), interval[i], porovnej_pair) - sint.begin();
    if (vysl[index]==-1) printf("OK\n");
    else printf("%d\n", vysl[index]);
  }
  printf("\n");
  return true;
}

int main() {
  while (solve());
  return 0;
}