#include <stdio.h>
#include <string.h>
#include <stdlib.h>

int main()
{
    int k,a,b;

    scanf("%d",&k);

    scanf("%d %d",&a,&b);

    int s = 0;

    while(1)
    {
        s = s+ k;
        

        if(a<=s && s<=b)
        {
            printf("OK\n");
            break;
        }

        if(b < s )
        {
            printf("NG\n");
            break;
        }

    }

    return 0;
}