#include<cassert>
#include<iostream>
#include<cstdio>
#include<vector>
#include<algorithm>
#include<cmath>
#include<map>
#include<set>
#include<queue>
#include<cstring>
#include<sstream>
#define FORE(it, c) for(__typeof((c).begin()) it = (c).begin(); it != (c).end(); ++it)
#define FC(aa, bb) FORE(bb, aa)
#define debug(x) cerr << #x << " = " << x << endl;
#define debugv(x) cerr << #x << " = " ; FORE(it, (x)) cerr << *it << ", "; cerr << endl;
#define fup(i, a, b) for(int i = (a); i <= (b); ++i)
#define fdo(i, a, b) for(int i = (a); i >= (b); --i)
#define FOR fup
#define FORD fdo
#define REP(i, n) for(int i = 0; i < (n); ++i)
#define ALL(x) (x).begin(), (x).end()
#define CLR(x) memset((x), 0, sizeof(x))
#define MP make_pair
#define PB push_back
#define siz(a) ((int)(a).size())
#define SZ siz
#define inf 1000000000
#define FI first
#define SE second

using namespace std;

typedef long long lli;
typedef double ld;
typedef lli LL;
typedef ld LD;
typedef vector<int> VI;
typedef pair<int, int> PII;

const int MAXN = 1000100;
int tab[MAXN];
int res[MAXN];

bool solve() {
    map<int,int> M;
    int n,q;
    if (scanf("%d%d", &n, &q) != 2) return false;
    if (n == 0) return false;
   // printf("%d %d\n", n, q);
    REP(i, n) {
        scanf("%d", &tab[i]);
        res[i] = inf;
    }
    int i = 0;
    REP(j, n) {
        while(i < n && siz(M) == i-j) {
            if (M.find(tab[i]) != M.end()) {
                M[tab[i]]++;
            } else M[tab[i]] = 1;
            ++i;
        }
        if (i == n) break;
        //printf("%d -> %d (%d %d)\n", j, res[j], i-j, siz(M));
        res[j] = i-1;
        int ile = M[tab[j]];
        if (ile == 1) M.erase(tab[j]);
        else M[tab[j]] = ile-1;
    }
    REP(i, q) {
        int a, b;
        scanf("%d%d", &a, &b);
        --a;--b;
        if (b < res[a]) {
            printf("OK\n");
            
        } else printf("%d\n", tab[res[a]]);
    }
    printf("\n");


    return true;
};

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