#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> tarjanScc(const Graph &g){
    int n = g.size(), idx = 0, k = 0, s = 0;
    vector<int> index(n, -1), lowlink(n), onStack(n), cmp(n), stk(n);
    function<void(int)> strongconnect;
    strongconnect = [&](int v){
        index[v] = lowlink[v] = idx++;
        stk[s++] = v; onStack[v] = true;
        for(auto &e : g[v]){
            int w = e.dst;
            if(index[w] == -1){
                strongconnect(w);
                lowlink[v] = min(lowlink[v], lowlink[w]);
            } else if(onStack[w]){
                lowlink[v] = min(lowlink[v], index[w]);
            }
        }
        if(lowlink[v] == index[v]){
            int w;
            do {
                w = stk[--s]; onStack[w] = false; cmp[w] = k;
            } while(w != v);
            ++k;
        }
    };
    for(int v = 0; v < n; v++) if(index[v] == -1) strongconnect(v);
    return cmp;
};

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

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

    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 = tarjanScc(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';
    }
}