// '-.-'
// () __.'.__
// .-:--:-. |_______|
// () \____/ \=====/
// /\ {====} )___(
// (\=, //\\ )__( /_____\
// __ |'-'-'| // .\ ( ) /____\ | |
// / \ |_____| (( \_ \ )__( | | | |
// \__/ |===| )) `\_) /____\ | | | |
// /____\ | | (/ \ | | | | | |
// | | | | | _.-'| | | | | | |
// |__| )___( )___( /____\ /____\ /_____\
// (====) (=====) (=====) (======) (======) (=======)
// }===={ }====={ }====={ }======{ }======{ }======={
// (______)(_______)(_______)(________)(________)(_________)
//
// Credits :- Joan G. Stark
//|~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~|
//| AUTHOR - KASPAROVIAN |
//|~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~|
#include<bits/stdc++.h>
#define rep(i,a,b) for(int i=(a);i<=(b);i++)
#define per(i,a,b) for(int i=(a);i>=(b);i--)
#define frr(i,n) for(int i=0;i<(n);i++)
#define pb push_back
#define eb emplace_back
#define all(v) (v).begin(),(v).end()
#define fr first
#define sc second
#define mk make_pair
#define endl '\n'
#define MOD 1000000007
#define in insert
#define sz(x) (ll)(x).size()
#define mem(a,b) memset(a,b,sizeof(a))
//#define int long long
#define runtime() ((double)clock() / CLOCKS_PER_SEC)
#define fast ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0)
using namespace std;
#define TRACE
#ifdef TRACE
#define trace(...) __f(#__VA_ARGS__, __VA_ARGS__)
template <typename Arg1>
void __f(const char* name, Arg1&& arg1){
cerr << name << " : " << arg1 << endl;
}
template <typename Arg1, typename... Args>
void __f(const char* names, Arg1&& arg1, Args&&... args){
const char* comma = strchr(names + 1, ',');cerr.write(names, comma - names) << " : " << arg1<<" | ";__f(comma+1, args...);
}
#else
#define trace(...)
#endif
typedef long long ll;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef long double ld;
typedef pair<ll,ll> pl;
typedef pair<int,int> pi;
typedef pair<int,pi> ppi;
typedef vector<vi> graph;
template<class T> void mxi(T & a, const T & b) { a = max(a, b); }
template<class T> void mni(T & a, const T & b) { a = min(a, b); }
ld EPS=1e-9;
mt19937 RNG(chrono::steady_clock::now().time_since_epoch().count());
#define SHUF(v) shuffle(all(v), RNG);
// Use mt19937_64 for 64 bit random numbers.
void solve()
{
int n; cin>>n;
if(n%3==1)
{
cout<<"IMPOSSIBLE"; return ;
}
string s;
if(n%6==5)
{
s="1 3 1 3 2 ";
for(int i=5;i<n;i+=6)
{
s+="1 2 3 3 2 1 ";
}
// cout<<s<<endl; return;
}
else if(n%6==3)
{
s="1 2 3 ";
for(int i=3;i<n;i+=6)
{
s+="1 2 3 3 2 1 ";
}
// cout<<s<<endl; return;
}
else if(n%6==2)
{
s="2 3 ";
for(int i=2;i<n;i+=6)
{
s+="1 2 3 3 2 1 ";
}
// cout<<s<<endl; return;
}
else
{
assert(n%6==0);
s="";
for(int i=0;i<n;i+=6)
{
s+="1 2 3 3 2 1 ";
}
// cout<<s<<endl; return;
}
cout<<s[0]-'0';
for(int i=2;i<sz(s);i+=2)
{
if(s[i]==' ')break;
cout<<' '<<s[i]-'0';
}
}
signed main()
{
fast;
int t,tab;
t=1;
tab=t;
while(t--)
{
//cout<<"Case #"<<(tab-t)<<": ";
solve();
}
// cerr<<runtime();
}
//APPROACHING A QUESTION
//+ Think of binary search (max of min etc also if n<=2*10^5)
//+ Think of common dp states (Even if it appears as maths but constraints are small)
//+ Check constraints
//+ Keep calm and enjoy the question
//+ Be sure to remove MOD from binpow (if needed)
//+ Try bidirectional analysis for constructive questions
//+ If given some sequence try thinking of prefix sums
//+ If constraints are too large maybe its simple maths
//+ In questions with binary operations think of bits independently and also the change pattern
//+ If two or more binary operations are given mostly there is a relation between them and an arithmatic operator