#include<cstdio>
#include<cstdlib>
#include<iostream>
#include<set>
#include<map>
#include<stack>
#include<complex>
#include<algorithm>
#include<string>
#include<vector>
#include<queue>
#include<deque>


using namespace std;
// using namespace __gnu_cxx;

typedef long long ll;
typedef double db;
typedef vector<int> vi;
typedef vector<string> vs;
typedef pair<int,int> pii;

#define INF (1<<30)
#define PB push_back
#define FI first
#define SE second
#define REP(i,n) for(int (i)=0;(i)<(n);++(i))
#define FUP(i,a,b) for(int (i)=(a);(i)<=(b);++(i))
#define FDN(i,a,b) for(int (i)=(a);(i)>=(b);--(i))

struct Zap{
    int a,b;
    int id;
    int odp;
};

map<int,int> lst;
int tab[2000000];
Zap zaps[2000000];

bool cmp1(const Zap &a, const Zap &b){
    return (a.a == b.a ? a.b < b.b : a.a < b.a);
}

bool cmp2(const Zap &a, const Zap &b){
    return a.id < b.id;
}

int main(){
  while(true){
    lst.clear();
    int m,q;
    scanf("%d%d", &m, &q);

    if(m==0 && q==0) break;

    REP(i,m){
        scanf("%d", &tab[i]);
    }
    REP(i,q){
        scanf("%d%d", &zaps[i].a, &zaps[i].b);
        zaps[i].id = i;
        zaps[i].odp = -1;
    }

    sort(zaps, zaps+q, cmp1);

    int w = 0;
    queue<int> kol;
    REP(i,m){
        int curr = tab[i];
        if(lst.find(curr) != lst.end()){ // jest
            int gdzie = lst[curr];
            while(!kol.empty()){
                int czub = kol.front();
                if(zaps[czub].a <= gdzie){
                    if(zaps[czub].b >= i+1){
                        zaps[czub].odp = curr;
                    }
                    kol.pop();
                } else {
                    break;
                }
            }
        }
        lst[curr] = i+1;

        while(w < q && zaps[w].a >= i+1){
            kol.push(w);
            w++;
        }
    }

    sort(zaps, zaps+q, cmp2);
    REP(i,q){
        if(zaps[i].odp == -1) printf("OK\n");
        else printf("%d\n", zaps[i].odp);
    }
    printf("\n");

  }
    return 0;
}