public static void main ( String [ ] args ) {
  int n = sc . nextInt ( ) ;
  String s = sc . next ( ) ;
  int x = 0 ;
  int ans = 0 ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) {
    if ( s . charAt ( i ) == 'I' ) {
      x ++ ;
    }
    else if ( s . charAt ( i ) == 'D' ) {
      x -- ;
    }
    ans = Math . max ( ans , x ) ;
  }
  System . out . println ( ans ) ;
}

public static void main ( String [ ] args ) { int n = sc . nextInt ( ) ; String s = sc . next ( ) ; int x = 0 ; int ans = 0 ; for ( int i = 0 ; i < n ; i ++ ) { if ( s . charAt ( i ) == ' I ' ) { x ++ ; } else if ( s . charAt ( i ) == ' D ' ) { x -- ; } ans = Math . max ( ans , x ) ; } System . out . println ( ans ) ; }
(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: (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) value: (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: (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: (block (if_statement condition: (parenthesized_expression (binary_expression left: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier))) right: (character_literal))) consequence: (block (expression_statement (update_expression (identifier)))) alternative: (if_statement condition: (parenthesized_expression (binary_expression left: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier))) right: (character_literal))) consequence: (block (expression_statement (update_expression (identifier)))))) (expression_statement (assignment_expression left: (identifier) right: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier) (identifier))))))) (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (identifier))))))