#include<stdio.h>

 #include<string.h>

 #include<iostream>

 #include<map>

 #define inf 0x3f3f3f3f

 using namespace std;

 map<int, int>mp;

 int num[];

 int id[];

 int main()

 {

     int n, q;

     while(cin >> n >> q)

     {

         if (n ==  && q == ) break;

         for (int i=; i<n; ++i)

         {

             cin >> num[i];

         }

         mp.clear();

         id[n] = inf;

         for (int i=n-; i>=; --i)

         {

             if (mp[num[i]] == )

             {

                 id[i] = id[i+];

                 mp[num[i]] = i;

                 continue;

             }

             else

             {

                id[i] = min(mp[num[i]], id[i+]);

                mp[num[i]] = i;

             }

         }

         while(q--)

         {

             int x, y;

             cin >> x >> y;

             x--;

             y--;

             if (y < id[x]) cout << "OK\n";

             else cout << num[id[x]] << endl;

         }

         cout << endl;

     }

     return ;

 }