#include<stdio.h>
int main(){
    int a, t;
    scanf("%d", &a);
    int b, c;
    scanf("%d %d", &b, &c);
    t = c / a;
    a = a * t;
    if(a >= b && a <= c)
        printf("OK\n");
    else
        printf("NG\n");
    return 0;
}