public static void main ( String [ ] args ) {
  Scanner sc = new Scanner ( System . in ) ;
  int n = sc . nextInt ( ) ;
  String s [ ] = new String [ n ] ;
  boolean flag = true ;
  int c = 0 ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) s [ i ] = sc . next ( ) ;
  for ( int i = 0 ;
  i < s [ 0 ] . length ( ) ;
  i ++ ) {
    for ( int j = 0 ;
    j < n - 1 ;
    j ++ ) {
      if ( s [ j ] . charAt ( i ) == s [ j + 1 ] . charAt ( i ) ) {
        continue ;
      }
      else {
        flag = false ;
        break ;
      }
    }
    if ( flag ) {
      c ++ ;
    }
    else {
      break ;
    }
  }
  System . out . println ( c ) ;
}

public static void main ( String [ ] args ) { Scanner sc = new Scanner ( System . in ) ; int n = sc . nextInt ( ) ; String s [ ] = new String [ n ] ; boolean flag = true ; int c = 0 ; for ( int i = 0 ; i < n ; i ++ ) s [ i ] = sc . next ( ) ; for ( int i = 0 ; i < s [ 0 ] . length ( ) ; i ++ ) { for ( int j = 0 ; j < n - 1 ; j ++ ) { if ( s [ j ] . charAt ( i ) == s [ j + 1 ] . charAt ( i ) ) { continue ; } else { flag = false ; break ; } } if ( flag ) { c ++ ; } else { break ; } } System . out . println ( c ) ; }
(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: (type_identifier) declarator: (variable_declarator name: (identifier) dimensions: (dimensions) value: (array_creation_expression type: (type_identifier) dimensions: (dimensions_expr (identifier))))) (local_variable_declaration type: (boolean_type) declarator: (variable_declarator name: (identifier) value: (true))) (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: (identifier)) update: (update_expression (identifier)) body: (expression_statement (assignment_expression left: (array_access array: (identifier) index: (identifier)) right: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list))))) (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: (binary_expression left: (identifier) right: (decimal_integer_literal))) update: (update_expression (identifier)) body: (block (if_statement condition: (parenthesized_expression (binary_expression left: (method_invocation object: (array_access array: (identifier) index: (identifier)) name: (identifier) arguments: (argument_list (identifier))) right: (method_invocation object: (array_access array: (identifier) index: (binary_expression left: (identifier) right: (decimal_integer_literal))) name: (identifier) arguments: (argument_list (identifier))))) consequence: (block (continue_statement)) alternative: (block (expression_statement (assignment_expression left: (identifier) right: (false))) (break_statement))))) (if_statement condition: (parenthesized_expression (identifier)) consequence: (block (expression_statement (update_expression (identifier)))) alternative: (block (break_statement))))) (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (identifier))))))