public static void main ( String [ ] args ) throws IOException {
  BufferedReader reader = new BufferedReader ( new InputStreamReader ( System . in ) ) ;
  int n = Integer . parseInt ( reader . readLine ( ) ) ;
  int [ ] array = new int [ n ] ;
  int [ ] farward = new int [ n ] ;
  StringTokenizer stoken = new StringTokenizer ( reader . readLine ( ) ) ;
  array [ 0 ] = Integer . parseInt ( stoken . nextToken ( ) ) ;
  farward [ 0 ] = 1 ;
  for ( int i = 1 ;
  i < n ;
  i ++ ) {
    array [ i ] = Integer . parseInt ( stoken . nextToken ( ) ) ;
    farward [ i ] = Math . min ( farward [ i - 1 ] + 1 , array [ i ] ) ;
  }
  int [ ] backward = new int [ n ] ;
  backward [ n - 1 ] = 1 ;
  int res = Math . min ( farward [ n - 1 ] , backward [ n - 1 ] ) ;
  for ( int i = n - 2 ;
  i > - 1 ;
  i -- ) {
    backward [ i ] = Math . min ( backward [ i + 1 ] + 1 , array [ i ] ) ;
    res = Math . max ( res , Math . min ( farward [ i ] , backward [ i ] ) ) ;
  }
  System . out . println ( res ) ;
}

public static void main ( String [ ] args ) throws IOException { BufferedReader reader = new BufferedReader ( new InputStreamReader ( System . in ) ) ; int n = Integer . parseInt ( reader . readLine ( ) ) ; int [ ] array = new int [ n ] ; int [ ] farward = new int [ n ] ; StringTokenizer stoken = new StringTokenizer ( reader . readLine ( ) ) ; array [ 0 ] = Integer . parseInt ( stoken . nextToken ( ) ) ; farward [ 0 ] = 1 ; for ( int i = 1 ; i < n ; i ++ ) { array [ i ] = Integer . parseInt ( stoken . nextToken ( ) ) ; farward [ i ] = Math . min ( farward [ i - 1 ] + 1 , array [ i ] ) ; } int [ ] backward = new int [ n ] ; backward [ n - 1 ] = 1 ; int res = Math . min ( farward [ n - 1 ] , backward [ n - 1 ] ) ; for ( int i = n - 2 ; i > - 1 ; i -- ) { backward [ i ] = Math . min ( backward [ i + 1 ] + 1 , array [ i ] ) ; res = Math . max ( res , Math . min ( farward [ i ] , backward [ i ] ) ) ; } System . out . println ( res ) ; }
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(for_statement init: (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (binary_expression left: (identifier) right: (decimal_integer_literal)))) condition: (binary_expression left: (identifier) right: (unary_expression operand: (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 (binary_expression left: (array_access array: (identifier) index: (binary_expression left: (identifier) right: (decimal_integer_literal))) right: (decimal_integer_literal)) (array_access array: (identifier) index: (identifier)))))) (expression_statement (assignment_expression left: (identifier) right: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier) (method_invocation object: 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