#include <iostream>
#include<vector>
#include <set>

using namespace std;

int app(istream &f)
{
 unsigned int M;
 unsigned int Q;
 
 string temp;

 for (;;)
 {
   f >> M >> Q;
   if (M == 0 && Q == 0) return 0;

   vector<unsigned int> be(M);
   vector<unsigned int> kezd(Q);
   vector<unsigned int> veg(Q);
   vector<int> ret(Q,-1);

   for (unsigned int i=0;i<M;i++)
   {
     f >> be[i]; 
   }
   for (unsigned int i=0;i<Q;i++)
   {
     f >> kezd[i] >> veg[i] ;
     kezd[i]--;
     veg[i]--;     
   }
   
   for (unsigned int j=0;j<Q;j++)
   {
	set<int> h;
  	for (unsigned int i=0;i<M;i++)
	{
		if (ret[j] == -1)
		{
			if (kezd[j]<=i && i<=veg[j])
			{
				if (h.count(be[i]) > 0) ret[j] = be[i];
				else h.insert(be[i]);
			}
		}
	}
   }

  for (unsigned int i=0;i<Q;i++)
   {
     if (ret[i] == -1) cout << "OK" << endl;
     else cout<< ret[i] << endl;
   }

   cout << endl;
   getline(f,temp);	
 }
 return 0;

}


int main()
{
  app(cin);

  return 0;
}