#include<stdio.h>
int main(void){
   int A,B,K;
   int i;
   int count=0;
    scanf("%d",&K);
    scanf("%d %d",&A,&B);

     for(i=K;i<A;i += K){
        if (i%K==0){
           count++;
        }
     }
     if(count==0){
        printf("OK\n");
     }else{
        printf("NG\n");
     }
     return 0;
}
     