#include<stdio.h>
#include<string.h>
int main()
{
int j,i,a,b,c,count=0;
scanf("%d %d %d",&i,&a,&b);
for(j=1;j<=100;j++)
{
c=i*j;
if(c>=a && c<=b)
 {
 printf("Ok\n");
 count=count+1;
 break;
 }
}
if(count==0)
printf("NG\n");
return 0;
}