#include <algorithm>

#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>

#include <string>
#include <vector>
#include <map>
#include <set>

using namespace std;

typedef pair< int, int > par;
#define x first
#define y second

#define FORC(it, V) for(__typeof((V).begin()) it = (V).begin(); it != (V).end(); ++it)

const int MAXN = 1000005;

int a[MAXN], p[MAXN], k[MAXN];
int ans[MAXN];
par e[2*MAXN];

struct cmp {
  bool operator() ( const int &a, const int &b ) {
    if( p[a] != p[b] ) return p[a] < p[b];
    if( k[a] != k[b] ) return k[a] < k[b];
    return a < b;
  }
};

set< int, cmp > S;
map< int, int > M;

int main(void)
{
  int n, q;
  while( scanf( "%d %d", &n, &q ) == 2 ) {
    if( n == 0 && q == 0 ) break;
  
    M.clear(), S.clear();
    for( int i = 0; i < n; ++i )
      scanf( "%d", a+i );

    int c = 0;
    for( int i = 0; i < q; ++i ) {
      scanf( "%d %d", p+i, k+i );
      --p[i], --k[i];
      e[c++] = par( p[i], i );
      e[c++] = par( k[i]+1, i );
      ans[i] = -1;
    }

    sort( e, e + c );

    int w = 0;
    for( int i = 0; i < n; ++i ) {
      while( w < c && e[w].x <= i ) {
	int j = e[w].y;
	if( p[j] == e[w].x ) S.insert( j ); else
	  S.erase( j );
	w++;
      }

      if( M.count(a[i]) ) {
	int l = M[ a[i] ];
	
	while( S.size() ) {
	  int x = *S.begin();
	  
	  if( p[x] > l ) break;
	  
	  ans[x] = a[i];
	  S.erase( S.begin() );
	}
      }

      M[ a[i] ] = i;
    }

    for( int i = 0; i < q; ++i )
      if( ans[i] == -1 ) puts( "OK" ); else
	printf( "%d\n", ans[i] );
    putchar( '\n' );
  }
  return 0;
}