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