#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
//using mint = modint1000000007;
//const int mod = 1000000007;
//using mint = modint998244353;
//const int mod = 998244353;
//const int INF = 1e9;
//const long long LINF = 1e18;
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep2(i,l,r)for(int i=(l);i<(r);++i)
#define rrep(i, n) for (int i = (n-1); i >= 0; --i)
#define rrep2(i,l,r)for(int i=(r-1);i>=(l);--i)
#define all(x) (x).begin(),(x).end()
#define allR(x) (x).rbegin(),(x).rend()
#define endl "\n"
#define P pair<int,int>
template<typename A, typename B> inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; }
template<typename A, typename B> inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; }

int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	int n; cin >> n;
	vector<string>s(n);
	rep(i, n)cin >> s[i];
	if (n > 52) {
		cout << "Impossible" << endl;
		return 0;
	}
	vector<string>x0(n), y0(n), x1(n), y1(n);
	rep(i, n) {
		x0[i] = s[i].substr(0, 2);
		y0[i] = s[i].substr(2, 1);
		x1[i] = s[i].substr(0, 1);
		y1[i] = s[i].substr(1, 2);
	}
	atcoder::two_sat ts(n);
	rep(i, n)rep2(j, i + 1, n) {
		// 00ng
		if (x0[i] == x0[j] || y0[i] == y0[j])ts.add_clause(i, true, j, true);
		// 01ng
		if (x0[i] == y1[j] || y0[i] == x1[j])ts.add_clause(i, true, j, false);
		// 10ng
		if (y1[i] == x0[j] || x1[i] == y0[j])ts.add_clause(i, false, j, true);
		// 11ng
		if (y1[i] == y1[j] || x1[i] == x1[j])ts.add_clause(i, false, j, false);
	}
	if (!ts.satisfiable()) {
		cout << "Impossible" << endl;
		return 0;
	}
	auto result = ts.answer();
	rep(i, n) {
		if (!result[i]) cout << x0[i] << " " << y0[i] << endl;
		else cout << x1[i] << " " << y1[i] << endl;
	}
	return 0;
}