Kolmijako

num = int(input())
sum1 = sum(range(num+1))
li = {}
def main():
    li = [x for x in range(1,num+1)]
    le = {}
    li1 = []
    li2 = []
    if sum1%3 != 0:
        print("IMPOSSIBLE")
        return
    aim = sum1//3
    num1 = 0
    for x in li[::-1]:
        if num1+x <= aim:
            le[x] = 1
            num1 += x
            li1.append(x)
            li.remove(x)
    num2 = 0
    for x in li[::-1]:
        if num2+x <= aim+1:
            le[x] = 2
            num2 += x
            li2.append(x)
            li.remove(x)
    l1 = sum(li1)
    l2 = sum(li2)
    l3 = sum(li)
    # 1 pienin, 3 suurin
    if l1 > l2 and l1 > l2:
        l1 = 3
        if l2 > l3:
            l2 = 2
            l3 = 1
        else:
            l3 = 2
            l2 = 1
    elif l2 > l1 and l2 > l3:
        l2 = 3
        if l1 > l3:
            l1 = 2
            l3 = 1
        else:
            l1 = 2
            l2 = 1
    else:
        l3 = 3
        if l1 > l2:
            l1 = 2
            l2 = 1
        else:
            l2 = 2
            l1 = 1
    test = " ".join(map(str,[le.get(x,3) for x in range(1,num+1)]))
    test = test.replace("1","p")
    test = test.replace("2","t")
    test = test.replace("3",str(l3))
    test = test.replace("p",str(l1))
    test = test.replace("t",str(l2))
    print(test)
main()

Test 1

Group: 1, 2

Verdict: ACCEPTED

Test 2

Group: 1, 2

Verdict: ACCEPTED

Test 3

Group: 1, 2

Verdict: ACCEPTED

Test 4

Group: 1, 2

Verdict: ACCEPTED

Test 5

Group: 1, 2

Verdict: ACCEPTED

Test 6

Group: 1, 2

Verdict: ACCEPTED

Test 7

Group: 1, 2

Verdict: ACCEPTED

Test 8

Group: 1, 2

Verdict: ACCEPTED

Test 9

Group: 2

Verdict: ACCEPTED

Test 10

Group: 2

Verdict: ACCEPTED

Test 11

Group: 2

Verdict: ACCEPTED

Test 12

Group: 2

Verdict: ACCEPTED

Test 13

Group: 2

Verdict: ACCEPTED

Test 14

Group: 2

Verdict: ACCEPTED

Test 15

Group: 2

Verdict: ACCEPTED