#include <stdio.h>
#include <stdlib.h>

int main(void){
    int     K,A,B;
    int     cnt=0;
    scanf("%d",&K);
    scanf("%d %d",&A,&B);
    for(A; A <= B; A++){
        if(A % K == 0){
            cnt = 1;
        }
    }
    if(cnt){printf("OK\n");}else printf("NG\n");
    return(0);
}