public static void main ( String [ ] args ) throws Exception {
  BufferedReader input = new BufferedReader ( new InputStreamReader ( System . in ) ) ;
  input . readLine ( ) ;
  String word = input . readLine ( ) ;
  int value = 0 ;
  int max = 0 ;
  for ( int i = 0 ;
  i < word . length ( ) ;
  i ++ ) {
    if ( word . charAt ( i ) == 'I' ) {
      value ++ ;
    }
    else {
      value -- ;
    }
    max = Math . max ( max , value ) ;
  }
  System . out . println ( max ) ;
}

public static void main ( String [ ] args ) throws Exception { BufferedReader input = new BufferedReader ( new InputStreamReader ( System . in ) ) ; input . readLine ( ) ; String word = input . readLine ( ) ; int value = 0 ; int max = 0 ; for ( int i = 0 ; i < word . length ( ) ; i ++ ) { if ( word . charAt ( i ) == ' I ' ) { value ++ ; } else { value -- ; } max = Math . max ( max , value ) ; } System . out . println ( max ) ; }
(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)))))))) (expression_statement (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: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list))) 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: (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))))))