Kolmijako

num = int(input())
sum1 = sum(range(num+1))
checks = [True for x in range(num+1)]
def main():
    if num == 3:
        print("1 2 3")
        return
    if (sum1)%3 != 0:
        print("IMPOSSIBLE")
        return
    aim = sum1//3
    li = {}
    num2 = 0
    last = 0
    for x in range(1,num+1)[::-1]:
        if x + num2 <= aim and aim-num2 >= x:
            last = x
            num2 += x
            li[x] = 1
        else:
            break
    save = aim-num2
    li[save] = 1
    num3 = 0
    for x in range(1,last)[::-1]:
        if x + num3 <= aim and aim-num3 >= x:
            if x != save:
                last = x
                num3 += x
                li[x] = 2
    print(" ".join(map(str,[li.get(x,3) for x in range(1,num+1)])))

main()

Test 1

Group: 1, 2

Verdict: ACCEPTED

Test 2

Group: 1, 2

Verdict: ACCEPTED

Test 3

Group: 1, 2

Verdict: WRONG ANSWER

Test 4

Group: 1, 2

Verdict: WRONG ANSWER

Test 5

Group: 1, 2

Verdict: ACCEPTED

Test 6

Group: 1, 2

Verdict: WRONG ANSWER

Test 7

Group: 1, 2

Verdict: WRONG ANSWER

Test 8

Group: 1, 2

Verdict: ACCEPTED

Test 9

Group: 2

Verdict: WRONG ANSWER

Test 10

Group: 2

Verdict: WRONG ANSWER

Test 11

Group: 2

Verdict: WRONG ANSWER

Test 12

Group: 2

Verdict: ACCEPTED

Test 13

Group: 2

Verdict: WRONG ANSWER

Test 14

Group: 2

Verdict: WRONG ANSWER

Test 15

Group: 2

Verdict: ACCEPTED