#include<stdio.h>
int main(){
    int k,a,b,d,i=1,o=0;
    scanf("%d%d%d",&k,&a,&b);
    while(1){
        d=k*i;
        i++;
        if(a<=d&&d<=b){
            o=1;
            break;
            
        }
        else if(b<=d){
            o=2;
            break;
        }
    }
    if(o==1)printf("OK\n");
    else if(o==2)printf("NG\n");
    return 0;
}