public static void main ( String [ ] args ) {
  Scanner in = new Scanner ( System . in ) ;
  int n = in . nextInt ( ) , m = in . nextInt ( ) ;
  List < Edge > list = new ArrayList < > ( ) ;
  int [ ] [ ] route = new int [ n ] [ n ] ;
  for ( int [ ] arr : route ) {
    Arrays . fill ( arr , INF ) ;
  }
  for ( int i = 0 ;
  i < n ;
  i ++ ) {
    route [ i ] [ i ] = 0 ;
  }
  for ( int k = 0 ;
  k < m ;
  k ++ ) {
    int u = in . nextInt ( ) - 1 , v = in . nextInt ( ) - 1 , l = in . nextInt ( ) ;
    if ( u == 0 || v == 0 ) {
      list . add ( new Edge ( u == 0 ? v : u , l ) ) ;
    }
    else {
      route [ u ] [ v ] = route [ v ] [ u ] = l ;
    }
  }
  for ( int k = 0 ;
  k < n ;
  k ++ ) {
    for ( int x = 0 ;
    x < n ;
    x ++ ) {
      for ( int y = 0 ;
      y < n ;
      y ++ ) {
        route [ x ] [ y ] = Math . min ( route [ x ] [ y ] , route [ x ] [ k ] + route [ k ] [ y ] ) ;
      }
    }
  }
  int ans = INF ;
  for ( Edge a : list ) {
    for ( Edge b : list ) {
      if ( a . to != b . to && route [ a . to ] [ b . to ] != INF ) {
        ans = Math . min ( ans , route [ a . to ] [ b . to ] + a . cost + b . cost ) ;
      }
    }
  }
  System . out . println ( ans == INF ? - 1 : ans ) ;
}

public static void main ( String [ ] args ) { Scanner in = new Scanner ( System . in ) ; int n = in . nextInt ( ) , m = in . nextInt ( ) ; List < Edge > list = new ArrayList < > ( ) ; int [ ] [ ] route = new int [ n ] [ n ] ; for ( int [ ] arr : route ) { Arrays . fill ( arr , INF ) ; } for ( int i = 0 ; i < n ; i ++ ) { route [ i ] [ i ] = 0 ; } for ( int k = 0 ; k < m ; k ++ ) { int u = in . nextInt ( ) - 1 , v = in . nextInt ( ) - 1 , l = in . nextInt ( ) ; if ( u == 0 || v == 0 ) { list . add ( new Edge ( u == 0 ? v : u , l ) ) ; } else { route [ u ] [ v ] = route [ v ] [ u ] = l ; } } for ( int k = 0 ; k < n ; k ++ ) { for ( int x = 0 ; x < n ; x ++ ) { for ( int y = 0 ; y < n ; y ++ ) { route [ x ] [ y ] = Math . min ( route [ x ] [ y ] , route [ x ] [ k ] + route [ k ] [ y ] ) ; } } } int ans = INF ; for ( Edge a : list ) { for ( Edge b : list ) { if ( a . to != b . to && route [ a . to ] [ b . to ] != INF ) { ans = Math . min ( ans , route [ a . to ] [ b . to ] + a . cost + b . cost ) ; } } } System . out . println ( ans == INF ? - 1 : 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 (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))) declarator: (variable_declarator name: (identifier) value: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))) (local_variable_declaration type: (generic_type (type_identifier) (type_arguments (type_identifier))) declarator: (variable_declarator name: (identifier) value: (object_creation_expression type: (generic_type (type_identifier) (type_arguments)) arguments: (argument_list)))) (local_variable_declaration type: (array_type element: (integral_type) dimensions: (dimensions)) declarator: (variable_declarator name: (identifier) value: (array_creation_expression type: (integral_type) dimensions: (dimensions_expr (identifier)) dimensions: (dimensions_expr (identifier))))) (enhanced_for_statement type: (array_type element: (integral_type) dimensions: (dimensions)) name: (identifier) value: (identifier) body: (block (expression_statement (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier) (identifier)))))) (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 (expression_statement (assignment_expression left: (array_access array: (array_access array: (identifier) index: (identifier)) index: (identifier)) right: (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: (binary_expression left: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)) right: (decimal_integer_literal))) declarator: (variable_declarator name: (identifier) value: (binary_expression left: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)) right: (decimal_integer_literal))) declarator: (variable_declarator name: (identifier) value: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))) (if_statement condition: (parenthesized_expression (binary_expression left: (binary_expression left: (identifier) right: (decimal_integer_literal)) right: (binary_expression left: (identifier) right: (decimal_integer_literal)))) consequence: (block (expression_statement (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (object_creation_expression type: (type_identifier) arguments: (argument_list (ternary_expression condition: (binary_expression left: (identifier) right: (decimal_integer_literal)) consequence: (identifier) alternative: (identifier)) (identifier))))))) alternative: (block (expression_statement (assignment_expression left: (array_access array: (array_access array: (identifier) index: (identifier)) index: (identifier)) right: (assignment_expression left: (array_access array: (array_access array: (identifier) index: (identifier)) index: (identifier)) right: (identifier)))))))) (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 (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 (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 (expression_statement (assignment_expression left: (array_access array: (array_access array: (identifier) index: (identifier)) index: (identifier)) right: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (array_access array: (array_access array: (identifier) index: (identifier)) index: (identifier)) (binary_expression left: (array_access array: (array_access array: (identifier) index: (identifier)) index: (identifier)) right: (array_access array: (array_access array: (identifier) index: (identifier)) index: (identifier))))))))))))) (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (identifier))) (enhanced_for_statement type: (type_identifier) name: (identifier) value: (identifier) body: (block (enhanced_for_statement type: (type_identifier) name: (identifier) value: (identifier) body: (block (if_statement condition: (parenthesized_expression (binary_expression left: (binary_expression left: (field_access object: (identifier) field: (identifier)) right: (field_access object: (identifier) field: (identifier))) right: (binary_expression left: (array_access array: (array_access array: (identifier) index: (field_access object: (identifier) field: (identifier))) index: (field_access object: (identifier) field: (identifier))) right: (identifier)))) consequence: (block (expression_statement (assignment_expression left: (identifier) right: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier) (binary_expression left: (binary_expression left: (array_access array: (array_access array: (identifier) index: (field_access object: (identifier) field: (identifier))) index: (field_access object: (identifier) field: (identifier))) right: (field_access object: (identifier) field: (identifier))) right: (field_access object: (identifier) field: (identifier))))))))))))) (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (ternary_expression condition: (binary_expression left: (identifier) right: (identifier)) consequence: (unary_expression operand: (decimal_integer_literal)) alternative: (identifier)))))))