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