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#include <bits/stdc++.h>
//#pragma GCC optimize("Ofast")
//#pragma GCC optimize ("unroll-loops")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")

//szablon czesciowo skopiowany z profilu https://codeforces.com/profile/Geothermal
using namespace std;
 
typedef long long LL;
typedef long double LD;
 
typedef pair<int, int> pii;
typedef pair<LL,LL> pll;
typedef pair<LD,LD> pdd;
 
typedef vector<int> vi;
typedef vector<bool> vb;
typedef vector<LD> vld;
typedef vector<LL> vll;
typedef vector<pii> vpii;
typedef vector<pll> vpll;
 
template<class T> using pq = priority_queue<T>;
template<class T> using pqg = priority_queue<T, vector<T>, greater<T>>;
 
#define rep(i, a, b) for (int i=a; i<(b); i++)
#define repd(i,a,b) for (int i = (a); i >= b; i--)
#define sz(x) (int)(x).size()
#define pb push_back
#define st first
#define nd second
#define lb lower_bound
#define ub upper_bound
#define all(x) x.begin(), x.end()
#define memo(x) memset(x, 0, sizeof(x))
#define debug(x) cerr << x << " "
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
LL losuj(LL a, LL b){ return a+rng()%(b-a+1);}

void solve(){
	int n; cin >> n;
	int cnt[]={0,0};
	rep(i,0,8*n){
		char x; cin >> x;
		cnt[(int)(x-'0')]++;
	}
	int diff = cnt[0] - cnt[1];
	if(diff&1){
		cout << "NIE\n";
		return;
	}
	int ocn = 0;
	if(diff >= 0){
		if(diff - 2*n > 0){
			cout << "NIE\n";
			return;
		}
		else{
			while(diff){
				diff-=2;
				ocn++;
				cout << 'a';
			}
			while(ocn < n){
				cout << 'c';
				ocn++;
			}
		}
	}
	else{
		if(diff + 4*n <0){
			cout << "NIE\n";
			return;
		}
		else{
			while(diff<0){
				if(diff == -2){
					cout << 'g';
					ocn++;
					diff+=2;
				}
				else{
					cout << 'w';
					ocn++;
					diff+=4;
				}
			}
			while(ocn < n){
				cout << 'c';
				ocn++;
			}
		}
	}
	cout << "\n";
}

int main(){
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	
	int t = 1;
	//cin >> t;
	while (t--) solve();
	
	return 0;
}