public static void main ( String [ ] args ) throws Exception {
  BufferedReader input = new BufferedReader ( new InputStreamReader ( System . in ) ) ;
  String [ ] letters = new String [ 3 ] ;
  for ( int i = 0 ;
  i < 3 ;
  i ++ ) {
    letters [ i ] = input . readLine ( ) ;
  }
  int current = 0 ;
  int [ ] positions = new int [ 3 ] ;
  while ( true ) {
    if ( positions [ current ] == letters [ current ] . length ( ) ) {
      System . out . println ( ( char ) ( current + 'A' ) ) ;
      break ;
    }
    current = letters [ current ] . charAt ( positions [ current ] ++ ) - 'a' ;
  }
}

public static void main ( String [ ] args ) throws Exception { BufferedReader input = new BufferedReader ( new InputStreamReader ( System . in ) ) ; String [ ] letters = new String [ 3 ] ; for ( int i = 0 ; i < 3 ; i ++ ) { letters [ i ] = input . readLine ( ) ; } int current = 0 ; int [ ] positions = new int [ 3 ] ; while ( true ) { if ( positions [ current ] == letters [ current ] . length ( ) ) { System . out . println ( ( char ) ( current + ' A ' ) ) ; break ; } current = letters [ current ] . charAt ( positions [ current ] ++ ) - ' a ' ; } }
(method_declaration (modifiers) type: (void_type) name: (identifier) parameters: (formal_parameters (formal_parameter type: (array_type element: (type_identifier) dimensions: (dimensions)) name: (identifier))) (throws (type_identifier)) body: (block (local_variable_declaration type: (type_identifier) declarator: (variable_declarator name: (identifier) value: (object_creation_expression type: (type_identifier) arguments: (argument_list (object_creation_expression type: (type_identifier) arguments: (argument_list (field_access object: (identifier) field: (identifier)))))))) (local_variable_declaration type: (array_type element: (type_identifier) dimensions: (dimensions)) declarator: (variable_declarator name: (identifier) value: (array_creation_expression type: (type_identifier) dimensions: (dimensions_expr (decimal_integer_literal))))) (for_statement init: (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (decimal_integer_literal))) condition: (binary_expression left: (identifier) right: (decimal_integer_literal)) update: (update_expression (identifier)) body: (block (expression_statement (assignment_expression left: (array_access array: (identifier) index: (identifier)) right: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))))) (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (decimal_integer_literal))) (local_variable_declaration type: (array_type element: (integral_type) dimensions: (dimensions)) declarator: (variable_declarator name: (identifier) value: (array_creation_expression type: (integral_type) dimensions: (dimensions_expr (decimal_integer_literal))))) (while_statement condition: (parenthesized_expression (true)) body: (block (if_statement condition: (parenthesized_expression (binary_expression left: (array_access array: (identifier) index: (identifier)) right: (method_invocation object: (array_access array: (identifier) index: (identifier)) name: (identifier) arguments: (argument_list)))) consequence: (block (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (cast_expression type: (integral_type) value: (parenthesized_expression (binary_expression left: (identifier) right: (character_literal))))))) (break_statement))) (expression_statement (assignment_expression left: (identifier) right: (binary_expression left: (method_invocation object: (array_access array: (identifier) index: (identifier)) name: (identifier) arguments: (argument_list (update_expression (array_access array: (identifier) index: (identifier))))) right: (character_literal))))))))