#include using namespace std; const int MAXN = 52; int N; string S[ MAXN * 2 ]; vector< int > G[ MAXN * 2 ], rG[ MAXN * 2 ]; void dfs_topo( int u, vector< int > &stk, vector< int > &vis ) { for( int v : G[ u ] ) { if( vis[ v ] ) continue; vis[ v ] = 1; dfs_topo( v, stk, vis ); } stk.emplace_back( u ); } void dfs_ksrj( int u, vector< int > &scc, int scc_id ) { for( int v : rG[ u ] ) { if( scc[ v ] ) continue; scc[ v ] = scc_id; dfs_ksrj( v, scc, scc_id ); } } signed main() { ios::sync_with_stdio( 0 ); cin >> N; if( N > MAXN ) { cout << "Impossible" << endl; exit( 0 ); } for( int i = 0; i < N; ++i ) { cin >> S[ i ]; } for( int i = 0; i < N; ++i ) { for( int j = 0; j < N; ++j ) { if( i == j ) continue; if( S[ i ][ 0 ] == S[ j ][ 0 ] or S[ i ].substr( 1, 2 ) == S[ j ].substr( 1, 2 ) ) { G[ i ].emplace_back( N + j ); rG[ N + j ].emplace_back( i ); } if( S[ i ][ 0 ] == S[ j ][ 2 ] or S[ i ].substr( 1, 2 ) == S[ j ].substr( 0, 2 ) ) { G[ i ].emplace_back( j ); rG[ j ].emplace_back( i ); } if( S[ i ][ 2 ] == S[ j ][ 0 ] or S[ i ].substr( 0, 2 ) == S[ j ].substr( 1, 2 ) ) { G[ N + i ].emplace_back( N + j ); rG[ N + j ].emplace_back( N + i ); } if( S[ i ][ 2 ] == S[ j ][ 2 ] or S[ i ].substr( 0, 2 ) == S[ j ].substr( 0, 2 ) ) { G[ N + i ].emplace_back( j ); rG[ j ].emplace_back( N + i ); } } } int scc_cnt = 0; vector< int > stk, scc( N * 2 ); { vector< int > vis( N * 2 ); for( int i = 0; i < N * 2; ++i ) { if( vis[ i ] ) continue; vis[ i ] = 1; dfs_topo( i, stk, vis ); } for( int i = N * 2 - 1; i >= 0; --i ) { if( scc[ stk[ i ] ] ) continue; scc[ stk[ i ] ] = ++scc_cnt; dfs_ksrj( stk[ i ], scc, scc_cnt ); } } for( int i = 0; i < N; ++i ) { if( scc[ i ] == scc[ N + i ] ) { cout << "Impossible" << endl; exit( 0 ); } } vector< int > sat( scc_cnt + 1 ); for( int i = N * 2 - 1; i >= 0; --i ) { int u = stk[ i ]; int v = stk[ i ] >= N ? stk[ i ] - N : stk[ i ] + N; if( sat[ scc[ u ] ] ) { sat[ scc[ v ] ] = 3 - sat[ scc[ u ] ]; } else if( sat[ scc[ v ] ] ) { sat[ scc[ u ] ] = 3 - sat[ scc[ v ] ]; } else { sat[ scc[ u ] ] = 1; sat[ scc[ v ] ] = 2; } } for( int i = 0; i < N; ++i ) { if( sat[ scc[ i ] ] == 1 ) { cout << S[ i ][ 0 ] << " " << S[ i ].substr( 1, 2 ) << "\n"; } else { cout << S[ i ].substr( 0, 2 ) << " " << S[ i ][ 2 ] << "\n"; } } return 0; }