def is_prime (x):
    if x == 1 :
        return False
    elif x == 2 :
        return True
    elif x == 0 :
        return False
    elif x % 2 ==0 and x >2:
        return False
    elif x % 3 == 0 and x >3:
        return False
    elif x % 5 == 0 and x >5:
        return False
    elif x % 7 == 0 and x >7:
        return False
    else :
        return True