#define debug if(0)
#include <cstdio>
#include <cstring>
#include <map>
#include <algorithm>
using namespace std;

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

struct query{
	int b,e,id;
	bool operator<(const query& rhs) const { return e < rhs.e; }
};

const int maxn = 1000100;
int n,m;
query q[maxn];
int t[maxn];
int res[maxn];
map<int,int> s;

int main() {
	while(true) { 
		scanf("%d%d", &n, &m);
		if(n == 0 && m == 0) break;
		s.clear();
		FOR(i,1,n) scanf("%d", t + i);
		REP(i,m) {
			scanf("%d %d", &q[i].b, &q[i].e);
			q[i].id = i;
		}
		sort(q, q + m);
		
		int f = 0;
		int j = 0;
		int ex = -2;
		
		FOR(i,1,n) {
			if(s.find(t[i]) != s.end()) {
				int nf = s[t[i]] + 1;
				if(nf > f) {
					f = nf;
					ex = t[i];
				}
			}
			s[t[i]] = i;
			
			debug printf("i %d f %d\n", i, f);
			while(j < m && q[j].e == i) {
				debug printf("proc id %d\n", q[j].id);
				if(q[j].b < f) res[q[j].id] = ex;
				else res[q[j].id] = -1;
				j++;
			}
		}
		
		REP(i,m) if(res[i] == -1) printf("OK\n");
				else printf("%d\n", res[i]);
		printf("\n");
	}
	return 0;
}