#include <stdio.h>

int main()
{
    int k, z, a, b, checker = 0, num[1001] = {0};
    scanf("%d", &k);
    scanf("%d %d", &a, &b);
    int difference = b - a;

    //bikin range
    for (int i = 0; i <= difference; i++)
    {
        num[a-1] = a;
        if (num[a-1] % k == 0)
        {
            checker = 1;
            break;
        }
        a++;
    }
    checker == 1 ? printf("OK\n") : printf("NG\n");

    return 0;
}