#include<stdio.h>
int main()
{
    int a,b,k,i,c;

    while(scanf("%d",&k)!=EOF)
    {
        scanf("%d %d",&a,&b);
        c = 1;
        for(i=a;i<=b;i++)
        {
            if(i%k==0)
            {
                c = 0;
                break;
            }
        }

        if(c)
            printf("NG\n");
        else
            printf("OK\n");
    }

    return 0;
}
