#include <bits/stdc++.h>
#define FOR(v, a, b) for(int v = (a); v < (b); ++v)
#define FORE(v, a, b) for(int v = (a); v <= (b); ++v)
#define REP(v, n) FOR(v, 0, n)
#define REPE(v, n) FORE(v, 0, n)
#define REV(v, a, b) for(int v = (a); v >= (b); --v)
#define ALL(x) (x).begin(), (x).end()
#define ITR(it, c) for(auto it = (c).begin(); it != (c).end(); ++it)
#define RITR(it, c) for(auto it = (c).rbegin(); it != (c).rend(); ++it)
#define EXIST(c,x) ((c).find(x) != (c).end())
#define LLI long long int
#define fst first
#define snd second

#ifdef DEBUG
#include <misc/C++/Debug.cpp>
#else
#define dump(x) ((void)0)
#endif

#define gcd __gcd

using namespace std;
template <class T> constexpr T lcm(T m, T n){return m/gcd(m,n)*n;}

template <typename I> void join(ostream &ost, I s, I t, string d=" "){for(auto i=s; i!=t; ++i){if(i!=s)ost<<d; ost<<*i;}ost<<endl;}
template <typename T> istream& operator>>(istream &is, vector<T> &v){for(auto &a : v) is >> a; return is;}
template <typename T, typename U> istream& operator>>(istream &is, pair<T,U> &p){is >> p.first >> p.second; return is;}

template <typename T, typename U> bool chmin(T &a, const U &b){return (a>b ? a=b, true : false);}
template <typename T, typename U> bool chmax(T &a, const U &b){return (a<b ? a=b, true : false);}
template <typename T, size_t N, typename U> void fill_array(T (&a)[N], const U &v){fill((U*)a, (U*)(a+N), v);}


class TwoSat{
  int n;
  vector<vector<int>> g, rg;

  int f(int i){
    assert(i != 0);
    assert(abs(i) <= n);
    if(i > 0) return i-1;
    else return abs(i)-1 + n;
  }

public:
  TwoSat(int n): n(n), g(2*n), rg(2*n){}

  /**
   * @brief a∨bの規則を導入する
   */
  void add(int a, int b){
    if(a == b){ // a ∨ a <=> (!a => a)
      g[f(-a)].push_back(f(a));
      rg[f(a)].push_back(f(-a));
    }else{ // a ∨ b <=> (!a => b) ∧ (!b => a)
      g[f(-a)].push_back(f(b));
      g[f(-b)].push_back(f(a));
      rg[f(b)].push_back(f(-a));
      rg[f(a)].push_back(f(-b));
    }
  }

  /**
   * @brief ¬(a∧b)の規則を導入する
   */
  void not_coexist(int a, int b){ // !(A ∧ B) <=> (!A ∨ !B)
    add(-a, -b);
  }

private:
  // scc用
  vector<bool> visit;
  vector<int> check;
  vector<int> scc;
  
  void dfs(int cur){
    visit[cur] = true;
    for(auto e : g[cur]){
      if(not visit[e]) dfs(e);
    }
    check.push_back(cur);
  }

  void rdfs(int cur, int i){
    scc[cur] = i;
    for(auto e : rg[cur]){
      if(scc[e] == -1) rdfs(e,i);
    }
  }

  vector<int> tsort(const vector<vector<int>> &graph){
    int n = graph.size();
    vector<int> indeg(n);
    REP(i,n){
      for(auto e : graph[i]){
        ++indeg[e];
      }
    }
  
    stack<int> st;
    REV(i,n-1,0){
      if(indeg[i] == 0) st.push(i);
    }

    vector<int> ret;
    while(!st.empty()){
      int cur = st.top(); st.pop();
      ret.push_back(cur);
      for(auto e : graph[cur]){
        --indeg[e];
        if(indeg[e]==0){
          st.push(e);
        }
      }
    }
  
    return ret;
  }
  
public:
  bool solve(vector<bool> &ret){
    visit.assign(2*n, false);
    scc.assign(2*n, -1);
    
    REP(i,2*n) if(!visit[i]) dfs(i);
    reverse(ALL(check));
    
    int m = 0;
    for(auto c : check) if(scc[c] == -1) {rdfs(c,m); ++m;}

    REP(i,n) if(scc[i] == scc[i+n]) return false;

    vector<vector<int>> g2(m);

    REP(i,n*2){
      for(auto j : g[i]){
        if(scc[i] != scc[j]) g2[scc[i]].push_back(scc[j]);
      }
    }

    auto ts = tsort(g2);

    vector<int> r(m);
    REP(i,m) r[ts[i]] = i;

    ret = vector<bool>(n);
    REP(i,n) ret[i] = r[scc[i]] > r[scc[i+n]];

    return true;
  }
};







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

  int N;
  while(cin >> N){
    vector<string> U(N); cin >> U;

    vector<string> S1(N), T1(N), S2(N), T2(N);
    REP(i,N){
      S1[i] = {U[i][0], U[i][1]};
      T1[i] = {U[i][2]};
      S2[i] = {U[i][0]};
      T2[i] = {U[i][1], U[i][2]};
    }

    TwoSat sat(N);

    set<char> cnt;
    for(auto &s : U) for(auto &c : s) cnt.insert(c);

    if((int)cnt.size() < N){
      cout << "Impossible" << endl;
      continue;
    }

    FORE(i,1,N){
      FORE(j,i+1,N){
        if(S1[i-1] == S1[j-1] or T1[i-1] == T1[j-1]) sat.not_coexist(i, j);
        if(S1[i-1] == T2[j-1] or T1[i-1] == S2[j-1]) sat.not_coexist(i, -j);
        if(S2[i-1] == T1[j-1] or T2[i-1] == S1[j-1]) sat.not_coexist(-i, j);
        if(S2[i-1] == S2[j-1] or T2[i-1] == T2[j-1]) sat.not_coexist(-i, -j);
      }
    }

    vector<bool> ret;
    bool ans = sat.solve(ret);

    if(ans){
      REP(i,N){
        if(ret[i]) cout << S1[i] << " " << T1[i] << endl;
        else cout << S2[i] << " " << T2[i] << endl;
      }
    }else{
      cout << "Impossible" << endl;
    }
  }
  
  return 0;
}