#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>

#define rep(i,k,n) for(int (i)=(k);(i)<(n);(i)++)
#define max(a,b) (a)>(b)?(a):(b)
#define min(a,b) (a)<(b)?(a):(b)
#define abs(a,b) (a)< 0 ?(a):-(a)
#define llong long long

int main(){
	int K; scanf("%d",&K);
	int A,B; scanf("%d %d",&A,&B);
	rep(i,A,B+1){
		if( i%K==0 ){
			printf("OK");
			return 0;
		}
	}
	printf("NG");
	return 0;
}
