#include <bits/stdc++.h> using namespace std; typedef signed long long ll; #undef _P #define _P(...) (void)printf(__VA_ARGS__) #define FOR(x,to) for(x=0;x<(to);x++) #define FORR(x,arr) for(auto& x:arr) #define ITR(x,c) for(__typeof(c.begin()) x=c.begin();x!=c.end();x++) #define ALL(a) (a.begin()),(a.end()) #define ZERO(a) memset(a,0,sizeof(a)) #define MINUS(a) memset(a,0xff,sizeof(a)) //------------------------------------------------------- int N; string S[101010],R[101010][2]; void solve() { int i,j,k,l,r,x,y; string s; cin>>N; if(N>52) return _P("Impossible\n"); FOR(i,N) cin>>S[i]; double start=clock(); srand(clock()); while(clock()-start<1.9*CLOCKS_PER_SEC) { int A[52]={}; set<string> SS; FOR(i,N) { A[i]=rand()%2; if(A[i]==0) { if(SS.count(S[i].substr(0,1))) goto out; if(SS.count(S[i].substr(1,2))) goto out; SS.insert(S[i].substr(0,1)); SS.insert(S[i].substr(1,2)); } else { if(SS.count(S[i].substr(2,1))) goto out; if(SS.count(S[i].substr(0,2))) goto out; SS.insert(S[i].substr(2,1)); SS.insert(S[i].substr(0,2)); } } FOR(i,N) { if(A[i]==0) cout<<S[i].substr(0,1)<<" "<<S[i].substr(1,2)<<endl; else cout<<S[i].substr(0,2)<<" "<<S[i].substr(2,1)<<endl; } return; out: ; } cout<<"Impossible"<<endl; } int main(int argc,char** argv){ string s;int i; if(argc==1) ios::sync_with_stdio(false), cin.tie(0); FOR(i,argc-1) s+=argv[i+1],s+='\n'; FOR(i,s.size()) ungetc(s[s.size()-1-i],stdin); solve(); return 0; }