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



    return 0;
}