#include<stdio.h>
int main()
  { 
    int K,A,B,count=0,i;
    scanf("%d %d %d",&K,&A,&B);
    for(i=A;i<=B;i++)
     { 
       if(i%K==0)
        { 
         count++;
        }
       }
  if(count>0)
    printf("OK");
  else
    printf("NG");
  return 0;
 }
