#include "bits/stdc++.h"
using namespace std;
#define FOR(i,j,k) for(int (i)=(j);(i)<(int)(k);++(i))
#define rep(i,j) FOR(i,0,j)
#define each(x,y) for(auto &(x):(y))
#define mp make_pair
#define mt make_tuple
#define all(x) (x).begin(),(x).end()
#define debug(x) cout<<#x<<": "<<(x)<<endl
#define smax(x,y) (x)=max((x),(y))
#define smin(x,y) (x)=min((x),(y))
#define MEM(x,y) memset((x),(y),sizeof (x))
#define sz(x) (int)(x).size()
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<ll> vll;
const string ALPHA="abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";

int N;
string U[100001];
map<string, int> ms;
set<string> us;
int x[52];

void ng() {
    cout << "Impossible" << endl;
    exit(0);
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    cin >> N;
    if(N > 52) ng();
    rep(i, N)cin >> U[i];

    rep(i, N) {
        ms[U[i].substr(0, 1)]++;
        ms[U[i].substr(1, 2)]++;
    }

    rep(hoge, 10000) {
        rep(i, N) {
            string s, t;
            s = U[i].substr(0, 1+x[i]), t = U[i].substr(1+x[i], 2-x[i]);
            int y = !x[i];
            string u = U[i].substr(0, 1 + y), v = U[i].substr(1 + y, 2 - y);
            cerr << s << ' ' << t << endl;
            if(ms[s] > 1 || ms[t] > 1) {
                ms[s]--; ms[t]--;
                if(!ms[u] && !ms[v])x[i] = y, ms[u]++, ms[v]++;
                else ms[s]++, ms[t]++;
            } else if(ms[s] == 1 && ms[t] == 1) {
                ms[s]--; ms[t]--;
                if(ms[u] == 0 && ms[v] == 0) {
                    y = rand() % 2;
                    U[i].substr(0, 1 + y), v = U[i].substr(1 + y, 2 - y);
                    ms[u]++; ms[v]++;
                } else ms[s]++, ms[t]++;
            }
        }
    }

    each(p, ms)if(p.second > 1)ng();

    rep(i, N)cout << U[i].substr(0, 1 + x[i]) << ' ' << U[i].substr(1 + x[i], 2 - x[i]) << endl;
}