#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <vector>
#include <map>

using namespace std;

#define REP(i,n) for(int i = 0; i < (n); ++i)

const int INF = 1000000000;

struct MaxTree {
    int *el, s;
    MaxTree(int size) {
        el = new int[2 * (s = 1 << size)];
        REP(x, 2*s) el[x] = 0;
    }
    
    ~MaxTree() {
        delete[] el;
    }
    
    void Set(int p, int v) {
        for(p += s, el[p] = v, p>>=1; p>0; p>>=1)
            el[p] = max(el[p << 1], el[(p<<1)+1]);
    }
    
    int Find(int p, int k) {
        int m = -INF;
        p += s;
        k += s;
        while(p<k) {
            if((p&1) == 1) m = max(m, el[p++]);
            if((k&1) == 0) m = max(m, el[k--]);
            p>>=1;
            k>>=1;
        }
        if(p == k) m = max(m, el[p]);
        return m;
    }
    
};


int main() {
    int M, Q, B, E, K;
    bool first = true;
    
    while(true) {        
        scanf("%d %d", &M, &Q);
        
        if(M == 0 && Q == 0) break;
        
        if(first) {
         first = false;
        } else {            
         printf("\n");
        }

        vector<int> seq;
        seq.reserve(M);

        map<int, int> mapa;

        int size = ceil(log(M)/log(2)+1);

        MaxTree tree(size);

        REP(i,M) {
            scanf("%d", &K);
            seq.push_back(K);
            map<int, int>::iterator it = mapa.find(K);
            int lp = 0;
            if(it == mapa.end()) {
                lp = 0;
            } else {
                lp = it->second;
            }
            mapa[K] = i + 1;
            tree.Set(i, lp);
        }

        REP(i,Q) {
            scanf("%d %d", &B, &E);
            //--B,--E;
            //printf("%d %d: \n", B, E);
            int mx = tree.Find(B-1, E-1);
            if(mx >= B && mx > 0) {
                printf("%d\n", seq[mx-1]);
            } else {
                printf("OK\n");
            }
        }
    }
    
    return 0;
}