#include<cassert>
#include<iostream>
#include<cstdio>
#include<vector>
#include<algorithm>
#include<cmath>
#include<map>
#include<set>
#include<queue>
#include<cstring>
#include<sstream>
#include <tr1/unordered_map>

#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;
using namespace tr1;

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

struct zap {
    int a, b, n;
    zap(int _a = 0, int _b = 0, int _n = 0) : a(_a), b(_b), n(_n) {}
    int operator<(const zap &x) const {
        return b < x.b;
    }
};

PII p[1000100];
int c[1000100], res[1000100];

int main(void) {
    while (1) {
        int n, q; scanf("%d%d", &n, &q);
        if (n == 0 && q == 0)
            break;
        REP (i, n)
            scanf("%d", &c[i]);
        unordered_map<int, int> last, prev;
        vector<zap> Q;
        REP (i, q) {
            int a, b; scanf("%d%d", &a, &b);
            --a; --b;
            Q.PB(zap(a, b, i));
            res[i] = -1;
        }
        sort(ALL(Q));
        int j = 0, mn = -1;
        REP (i, n) {
            if (last.find(c[i]) != last.end()) {
                prev[c[i]] = last[c[i]];
                if (mn == -1 || (prev[c[i]] > prev[mn]))
                    mn = c[i];
            }
            last[c[i]] = i;
            for (; j < SZ(Q) && Q[j].b == i; ++j) {
                if (prev[mn] >= Q[j].a)
                    res[Q[j].n] = mn;
            }
        }
        REP (i, q) {
            if (res[i] == -1)
                puts("OK");
            else
                printf("%d\n", res[i]);
        }
        puts("");
    }
    return 0;
}