#include<stdio.h>

int main(void){
    int A,B,K,x;
    scanf("%d",&K);
    scanf("%d %d",&A,&B);

    if(1<=A&&B<=1000&&1<=K&&K<=1000){
        for(int i=A;i<=B;i++){
            if(i%K == 0){
                x = 0;
                break;
            }else{
                x = 1;
            }
        }
        if(x == 0){
            printf("OK\n");
        }else if(x == 1){
            printf("NG\n");
        }
    }
    return 0;
}