#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;
 }
