#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define all(c) begin(c), end(c)
#define dump(x) cerr << __LINE__ << ":\t" #x " = " << x << endl

using Weight = int;
using Capacity = int;
struct Edge {
    int src, dst;
    Weight weight;
    Edge(int s, int d, Weight w) : src(s), dst(d), weight(w) {}
};
using Edges = vector<Edge>;
using Graph = vector<Edges>;
using Array = vector<Weight>;
using Matrix = vector<Array>;

vector<int> kosaraju(const Graph &g) {
    int n = g.size(), sz = 0;
    Graph rg(n);
    vector<int> stk, cmp(n, -1), added(n), visited(n), ord(n);
    for (auto &es : g) {
        for (auto &e : es) rg[e.dst].emplace_back(e.dst, e.src, e.weight);
        sz += es.size();
    }
    stk.resize(n + sz);
    sz = 0;
    for (int i = 0; i < n; i++) {
        if (visited[i]) continue;
        int s = 0;
        stk[s++] = i;
        while (s != 0) {
            int v = stk[s - 1];
            visited[v] = true;
            bool pushed = false;
            for (auto &e : g[v]) {
                int dst = e.dst;
                if (!visited[dst]) {
                    stk[s++] = dst;
                    pushed = true;
                }
            }
            if (pushed) continue;
            int t = stk[s - 1];
            if (!added[t]) {
                added[t] = true;
                ord[n - ++sz] = t;
            }
            --s;
        }
    }
    int k = 0;
    for (int &u : ord) {
        if (cmp[u] != -1) continue;
        int s = 0;
        stk[s++] = u;
        while (s != 0) {
            int v = stk[--s];
            cmp[v] = k;
            for (auto &e : rg[v]) {
                int d = e.dst;
                if (cmp[d] == -1) stk[s++] = d;
            }
        }
        ++k;
    }
    return cmp;
}

int main(){
    cin.tie(0);
    ios::sync_with_stdio(0);

    int n;
    cin >> n;
    if(n > 2756){
        cout << "Impossible" << endl;
        exit(0);
    }
    vector<string> ss(n);
    rep(i, n) cin >> ss[i];

    int nn = n+n;
    Graph g(nn);

    auto sep = [&](int u, int v){
        int iu = (u+n) % nn;
        int iv = (v+n) % nn;
        g[u].emplace_back(u, v, 1);
        g[iv].emplace_back(iv, iu, 1);
    };

    vector<string> a(n), ab(n), bc(n), c(n);
    rep(i, n){
        string &s = ss[i];
        a[i] = s.substr(0, 1);
        ab[i] = s.substr(0, 2);
        bc[i] = s.substr(1);
        c[i] = s.substr(2);
    }

    rep(i, n) rep(j, i){
        if(a[i] == a[j] || bc[i] == bc[j]) sep(i, j+n);
        if(a[i] == c[j] || bc[i] == ab[j]) sep(i, j);
        if(c[i] == a[j] || ab[i] == bc[j]) sep(i+n, j+n);
        if(c[i] == c[j] || ab[i] == ab[j]) sep(i+n, j);
    }

    vector<int> cmp = kosaraju(g);
    rep(i, n){
        if(cmp[i] == cmp[i+n]){
            cout << "Impossible" << '\n';
            exit(0);
        }
    }

    rep(i, n){
        if(cmp[i] < cmp[i+n]) cout << ab[i] << ' ' << c[i] << '\n';
        else cout << a[i] << ' ' << bc[i] << '\n';
    }
}