public static void main ( String [ ] args ) {
  Scanner sc = new Scanner ( System . in ) ;
  int n = sc . nextInt ( ) ;
  int m = sc . nextInt ( ) ;
  int [ ] [ ] V = new int [ n + 1 ] [ n + 1 ] ;
  for ( int i = 0 ;
  i < m ;
  i ++ ) {
    int a = sc . nextInt ( ) ;
    int b = sc . nextInt ( ) ;
    V [ a ] [ b ] = 1 ;
    V [ b ] [ a ] = 1 ;
  }
  Queue < Integer > q = new LinkedList < > ( ) ;
  q . add ( 1 ) ;
  int [ ] d = new int [ n + 1 ] ;
  while ( ! q . isEmpty ( ) ) {
    int vertex = q . poll ( ) ;
    for ( int i = 2 ;
    i <= n ;
    i ++ ) {
      if ( d [ i ] == 0 && V [ vertex ] [ i ] != V [ 1 ] [ n ] ) {
        d [ i ] = d [ vertex ] + 1 ;
        q . add ( i ) ;
      }
    }
  }
  if ( d [ n ] == 0 ) {
    System . out . println ( - 1 ) ;
  }
  else {
    System . out . println ( d [ n ] ) ;
  }
}

public static void main ( String [ ] args ) { Scanner sc = new Scanner ( System . in ) ; int n = sc . nextInt ( ) ; int m = sc . nextInt ( ) ; int [ ] [ ] V = new int [ n + 1 ] [ n + 1 ] ; for ( int i = 0 ; i < m ; i ++ ) { int a = sc . nextInt ( ) ; int b = sc . nextInt ( ) ; V [ a ] [ b ] = 1 ; V [ b ] [ a ] = 1 ; } Queue < Integer > q = new LinkedList < > ( ) ; q . add ( 1 ) ; int [ ] d = new int [ n + 1 ] ; while ( ! q . isEmpty ( ) ) { int vertex = q . poll ( ) ; for ( int i = 2 ; i <= n ; i ++ ) { if ( d [ i ] == 0 && V [ vertex ] [ i ] != V [ 1 ] [ n ] ) { d [ i ] = d [ vertex ] + 1 ; q . add ( i ) ; } } } if ( d [ n ] == 0 ) { System . out . println ( - 1 ) ; } else { System . out . println ( d [ n ] ) ; } }
(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)))) (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: (array_type element: (integral_type) dimensions: (dimensions)) declarator: (variable_declarator name: (identifier) value: (array_creation_expression type: (integral_type) dimensions: (dimensions_expr (binary_expression left: (identifier) right: (decimal_integer_literal))) dimensions: (dimensions_expr (binary_expression left: (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: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))) (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))) (expression_statement (assignment_expression left: (array_access array: (array_access array: (identifier) index: (identifier)) index: (identifier)) right: (decimal_integer_literal))) (expression_statement (assignment_expression left: (array_access array: (array_access array: (identifier) index: (identifier)) index: (identifier)) right: (decimal_integer_literal))))) (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)))) (expression_statement (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (decimal_integer_literal)))) (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 (binary_expression left: (identifier) right: (decimal_integer_literal)))))) (while_statement condition: (parenthesized_expression (unary_expression operand: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))) body: (block (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))) (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: (binary_expression left: (array_access array: (identifier) index: (identifier)) right: (decimal_integer_literal)) right: (binary_expression left: (array_access array: (array_access array: (identifier) index: (identifier)) index: (identifier)) right: (array_access array: (array_access array: (identifier) index: (decimal_integer_literal)) index: (identifier))))) consequence: (block (expression_statement (assignment_expression left: (array_access array: (identifier) index: (identifier)) right: (binary_expression left: (array_access array: (identifier) index: (identifier)) right: (decimal_integer_literal)))) (expression_statement (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier)))))))))) (if_statement condition: (parenthesized_expression (binary_expression left: (array_access array: (identifier) index: (identifier)) right: (decimal_integer_literal))) consequence: (block (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (unary_expression operand: (decimal_integer_literal)))))) alternative: (block (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (array_access array: (identifier) index: (identifier)))))))))