Split in Three

input/code.cpp: In function 'void solve()':
input/code.cpp:12:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d", &n);
     ~~~~~^~~~~~~~~~

#include <bits/stdc++.h>

using namespace std;

const int MAX_N = 100;

int t;
int n;

void solve()
{
    scanf("%d", &n);
    if(n % 3 == 1)
    {
        puts("IMPOSSIBLE");
    }
    else
    {
        int Groups[MAX_N];
        int Index[3] = {1, 2, 3}; // smallest, middle, highest
        if(n % 3 == 0)
        {
            Groups[0] = 1;
            Groups[1] = 2;
            Groups[2] = 3;
            for(int i = 3; i < n; i+=3)
            {
                Groups[i] = Index[2];
                Groups[i+1] = Index[0];
                Groups[i+2] = Index[1];
                swap(Index[1], Index[2]);
            }
        }
        else // n % 3 == 2
        {
            Groups[2] = 1;
            Groups[3] = 2;
            Groups[4] = 3;
            for(int i = 5; i < n; i+=3)
            {
                Groups[i] = Index[2];
                Groups[i+1] = Index[0];
                Groups[i+2] = Index[1];
                swap(Index[1], Index[2]);
            }
            Groups[0] = Index[0];
            Groups[1] = Index[1];
            swap(Index[1], Index[2]);
        }
        for(int i = 0; i < n; i++)
        {
            printf("%d ", Index[Groups[i]-1]);
        }
    }
}

int main()
{
    t = 1;
    //scanf("%d", &t);
    while(t--)
    {
        solve();
    }
    return 0;
}

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