#include <stdio.h>
#include <stdlib.h>
#include <algorithm>
#include <functional>
#include <string>
#include <vector>
#include <queue>
#include <stack>
#include <map>
#include <set>

using namespace std;

#define REP(i, N) for(int (i)=0; (i)<(N); (i)++)
#define ll long long
#define mp make_pair
#define pb push_back
int main() {
	int n;
	while(scanf("%d", &n) == 1) {
		bool ok = true;
		int mmax = 0;
		vector<int> A;
		A.pb(0);
		REP(i, n) {
			int x;
			scanf("%d", &x);
			A.pb(x);
			if(i >= 3 && ok) {
//				printf("%d %d %d %d\n", A[1], A[3], A[0], A[2]);
			//	printf("%d %d %d %d %d\n", A[0], A[1], A[2], A[3], A[4]);
				if(A[4]+A[0] >= A[2] && A[1] >= A[3]) {
					ok = false;	
					mmax = i;
				}
				A.erase(A.begin());
			}
			
		}
		if(ok) printf("OK\n");
		else printf("%d\n", mmax);

	}
	return 0;
}