import math
def f(n):
    n=n-1
    on = n
    if n < 0:
        return None
    else:
        list = []
        temp = []
        while n >= math.ceil(on/2):
            list.append("1"*(n-(on-n))+"2"*(on-n))
            n=n-1
        for x in list:
            if x.find("1") > -1 and  x.find("2") > -1:
                
    return list

print(f(10))