public static void main ( String [ ] args ) {
  Scanner sc = new Scanner ( System . in ) ;
  String [ ] strf = sc . nextLine ( ) . trim ( ) . split ( ":" ) ;
  String [ ] stre = sc . nextLine ( ) . trim ( ) . split ( ":" ) ;
  int hrf = Integer . valueOf ( strf [ 0 ] ) ;
  int mmf = Integer . valueOf ( strf [ 1 ] ) ;
  int hre = Integer . valueOf ( stre [ 0 ] ) ;
  int mme = Integer . valueOf ( stre [ 1 ] ) ;
  int t1 = hrf * 60 + mmf ;
  int t2 = hre * 60 + mme ;
  int t3 = ( t1 + t2 ) / 2 ;
  hrf = ( t3 ) / 60 ;
  mmf = ( t3 % 60 ) ;
  if ( ( hrf + "" ) . length ( ) == 1 ) {
    System . out . print ( "0" + hrf ) ;
  }
  else {
    System . out . print ( hrf ) ;
  }
  System . out . print ( ":" ) ;
  if ( ( mmf + "" ) . length ( ) == 1 ) {
    System . out . print ( "0" + mmf ) ;
  }
  else {
    System . out . print ( mmf ) ;
  }
}

public static void main ( String [ ] args ) { Scanner sc = new Scanner ( System . in ) ; String [ ] strf = sc . nextLine ( ) . trim ( ) . split ( " : " ) ; String [ ] stre = sc . nextLine ( ) . trim ( ) . split ( " : " ) ; int hrf = Integer . valueOf ( strf [ 0 ] ) ; int mmf = Integer . valueOf ( strf [ 1 ] ) ; int hre = Integer . valueOf ( stre [ 0 ] ) ; int mme = Integer . valueOf ( stre [ 1 ] ) ; int t1 = hrf * 60 + mmf ; int t2 = hre * 60 + mme ; int t3 = ( t1 + t2 ) / 2 ; hrf = ( t3 ) / 60 ; mmf = ( t3 % 60 ) ; if ( ( hrf + " " ) . length ( ) == 1 ) { System . out . print ( "0" + hrf ) ; } else { System . out . print ( hrf ) ; } System . out . print ( " : " ) ; if ( ( mmf + " " ) . length ( ) == 1 ) { System . out . print ( "0" + mmf ) ; } else { System . out . print ( mmf ) ; } }
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