#include<stdio.h>
int main()
{
    int K,A,B,i,mul;
    scanf("%d",&K);
    scanf("%d %d",&A,&B);
    mul=K;
    for(i=2;mul<=A;i++)
    {
       mul=K*i;

    }
   if(mul>=A && mul<=B)
       printf("OK");
       else
        printf("NG");
       return 0;


}
