public static void main ( String [ ] args ) {
  FastReader fr = new FastReader ( ) ;
  Scanner sc = new Scanner ( System . in ) ;
  int n = fr . nextInt ( ) ;
  int one = 0 , two = 0 ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) {
    int x = fr . nextInt ( ) ;
    if ( x == 1 ) one ++ ;
    else two ++ ;
  }
  if ( one == two ) System . out . print ( two ) ;
  else if ( one < two ) System . out . print ( one ) ;
  else {
    int ans = two ;
    one -= two ;
    ans += one / 3 ;
    System . out . print ( ans ) ;
  }
}

public static void main ( String [ ] args ) { FastReader fr = new FastReader ( ) ; Scanner sc = new Scanner ( System . in ) ; int n = fr . nextInt ( ) ; int one = 0 , two = 0 ; for ( int i = 0 ; i < n ; i ++ ) { int x = fr . nextInt ( ) ; if ( x == 1 ) one ++ ; else two ++ ; } if ( one == two ) System . out . print ( two ) ; else if ( one < two ) System . out . print ( one ) ; else { int ans = two ; one -= two ; ans += one / 3 ; System . out . print ( 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: (type_identifier) declarator: (variable_declarator name: (identifier) value: (object_creation_expression type: (type_identifier) arguments: (argument_list)))) (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: (integral_type) declarator: (variable_declarator name: (identifier) value: (decimal_integer_literal)) 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 (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))) (if_statement condition: (parenthesized_expression (binary_expression left: (identifier) right: (decimal_integer_literal))) consequence: (expression_statement (update_expression (identifier))) alternative: (expression_statement (update_expression (identifier)))))) (if_statement condition: (parenthesized_expression (binary_expression left: (identifier) right: (identifier))) consequence: (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (identifier)))) alternative: (if_statement condition: (parenthesized_expression (binary_expression left: (identifier) right: (identifier))) consequence: (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (identifier)))) alternative: (block (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (identifier))) (expression_statement (assignment_expression left: (identifier) right: (identifier))) (expression_statement (assignment_expression left: (identifier) right: (binary_expression left: (identifier) right: (decimal_integer_literal)))) (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (identifier)))))))))