#include <stdio.h>
int main(){
int a,b,k;
int i =1;
scanf("%d",&k);
scanf("%d %d",&a,&b);
if((a%k!= 0)&&(b%k!=0)&&(b-a < k)){
++i;
k *= i;
if(a<=k && k<=b){printf("OK");
break;}
else continue;}
else if(a%k == 0||b%k==0)printf("OK");
else if (b-a >= k)printf("OK");
else printf("NG");
}