public static void main ( String [ ] args ) {
  Scanner scan = new Scanner ( System . in ) ;
  int n = scan . nextInt ( ) ;
  String [ ] array = new String [ n ] ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) {
    array [ i ] = scan . next ( ) ;
  }
  int count = 0 ;
  for ( int i = 0 ;
  i < array [ 0 ] . length ( ) ;
  i ++ ) {
    for ( int j = 0 ;
    j < array . length ;
    j ++ ) {
      if ( array [ 0 ] . charAt ( i ) != array [ j ] . charAt ( i ) ) {
        System . out . println ( count ) ;
        return ;
      }
    }
    count ++ ;
  }
}

public static void main ( String [ ] args ) { Scanner scan = new Scanner ( System . in ) ; int n = scan . nextInt ( ) ; String [ ] array = new String [ n ] ; for ( int i = 0 ; i < n ; i ++ ) { array [ i ] = scan . next ( ) ; } int count = 0 ; for ( int i = 0 ; i < array [ 0 ] . length ( ) ; i ++ ) { for ( int j = 0 ; j < array . length ; j ++ ) { if ( array [ 0 ] . charAt ( i ) != array [ j ] . charAt ( i ) ) { System . out . println ( count ) ; return ; } } count ++ ; } }
(method_declaration (modifiers) type: (void_type) name: (identifier) parameters: (formal_parameters (formal_parameter type: (array_type element: (type_identifier) dimensions: (dimensions)) name: (identifier))) body: (block (local_variable_declaration type: (type_identifier) declarator: (variable_declarator name: (identifier) value: (object_creation_expression type: (type_identifier) arguments: (argument_list (field_access object: (identifier) field: (identifier)))))) (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))) (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 (identifier))))) (for_statement init: (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (decimal_integer_literal))) condition: (binary_expression left: (identifier) right: (identifier)) 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))) (for_statement init: (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (decimal_integer_literal))) condition: (binary_expression left: (identifier) right: (method_invocation object: (array_access array: (identifier) index: (decimal_integer_literal)) name: (identifier) arguments: (argument_list))) update: (update_expression (identifier)) body: (block (for_statement init: (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (decimal_integer_literal))) condition: (binary_expression left: (identifier) right: (field_access object: (identifier) field: (identifier))) update: (update_expression (identifier)) body: (block (if_statement condition: (parenthesized_expression (binary_expression left: (method_invocation object: (array_access array: (identifier) index: (decimal_integer_literal)) name: (identifier) arguments: (argument_list (identifier))) right: (method_invocation object: (array_access array: (identifier) index: (identifier)) name: (identifier) arguments: (argument_list (identifier))))) consequence: (block (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (identifier)))) (return_statement))))) (expression_statement (update_expression (identifier)))))))