#include<stdio.h>
int main()
{
    int k,a,b,mul,count=0;
    scanf("%d %d %d",&k,&a,&b);
    for(int i=1;i<=b;i++)
    {
        mul=k*i;
        if(mul>=a && mul<=b)
        {
            printf("OK\n");
            count++;break;
        }
    }
    if(count==0)
        printf("NG\n");
}
