#include <stdio.h>

int main(void){

    int a,b,k,key;

    scanf("%d\n%d %d",&k,&a,&b);

    for(;a<=b;a++){
        key = a%k;
        if(key == 0){
            printf("OK\n");
            return 0;
        }
    }
    printf("NG\n");

    return 0;

}