#include<stdio.h>
int main()
{
    int K,A,B,i=1,mul;
    scanf("%d %d %d",&K,&A,&B);
    while(1)
    {
       i++;
       mul=K*i;
   if(mul>=A&&mul<=B)
    break;
    }
    if(mul>=A&&mul<=B)
       printf("OK");
       else
        printf("NG");
       return 0;


}
