#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];
int R[101010][4];
int A[101010];
int SS[5050];
vector<int> V;

void dfs(int x) {
	int i;
	if(x==N) {
		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;
		}
		exit(0);
	}
	int d=V[x];
	int m=rand()%2;
	
	FOR(i,2) {
		if(i==m) {
			if(SS[R[d][0]]==0 && SS[R[d][1]]==0) {
				A[d]=0;
				SS[R[d][0]]=SS[R[d][1]]=1;
				dfs(x+1);
				SS[R[d][0]]=SS[R[d][1]]=0;
			}
		}
		else {
			if(R[d][3]!=R[d][1] && SS[R[d][2]]==0 && SS[R[d][3]]==0) {
				A[d]=1;
				SS[R[d][2]]=SS[R[d][3]]=1;
				dfs(x+1);
				SS[R[d][2]]=SS[R[d][3]]=0;
				
			}
		}
	}
	
	
}

void solve() {
	int i,j,k,l,r,x,y; string s;
	
	srand(clock());
	cin>>N;
	if(N>52) return _P("Impossible\n");
	FOR(i,N) {
		V.push_back(i);
		cin>>S[i];
		R[i][0]=S[i][0];
		R[i][1]=256+S[i][1]*(int)256+S[i][2];
		R[i][2]=S[i][2];
		R[i][3]=256+S[i][0]*(int)256+S[i][1];
	}
	random_shuffle(ALL(V));
	
	dfs(0);
	_P("Impossible\n");
}


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;
}