#include<stdio.h>

int main(){
  int k,a,b;
  scanf("%d %d %d",&k,&a,&b);
  
  int i;
  int res = 0;
  for(i = 1;i < 1000;i++){ 
    if(k*i >= a && k*i <= b)
     	res = 1;
  }
  if(k*0 >= a && k*0 <=b)
    res =1;
  if(res == 1)
    printf("OK");
  else
    printf("NG");
 
  return 0;
}
