How can I fix this error in expressjs in the view? [JADE]

views/factorial

extends layout

block content
	h1= title
	p Welcome to #{title}
	p Ingrese un numero
	form(method="POST", action="/factorial", name="myForm",onsubmit='return validateForm()')
		input(type='number', name='numero')
		input(type='submit', value='Enviar')

archive app.js

var express = require('express');
var path = require('path');
var favicon = require('serve-favicon');
var logger = require('morgan');
var cookieParser = require('cookie-parser');
//agregado
var bodyParser = require('body-parser');
var engine = require('ejs-mate');

var routes = require('./routes/index');
var users = require('./routes/users');

var app = express();

// instruct the app to use the 'bodyParser()' middleware for all routes
app.use(bodyParser());

// view engine setup
app.engine('ejs', engine);
app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'jade');


app.use(logger('dev'));
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: true }));
app.use(cookieParser());

app.use(express.static(path.join(__dirname, 'public')));
app.use(express.static(path.join(__dirname, 'bower_components')));

app.use('/', routes);
app.use('/users', users);

app.post('/factorial', function(req, res) {
  var num=req.body.numero;
  dd(num);
  for(var i=1;i<=num;i++)
    i=i*num;
  res.send('/factorial'+i);
});

// development error handler
// will print stacktrace
if (app.get('env') === 'development') {
  app.use(function(err, req, res, next) {
    res.status(err.status || 500);
    res.render('error', {
      message: err.message,
      error: err
    });
  });
}

// production error handler
// no stacktraces leaked to user
app.use(function(err, req, res, next) {
  res.status(err.status || 500);
  res.render('error', {
    message: err.message,
    error: {}
  });
});


module.exports = app;

routes/index.js

var express = require('express');
var router = express.Router();

/* GET home page. */
router.get('/', function(req, res, next) {
	res.render('index.jade', { title: 'Express' });
});


router.get('/factorial', function(req, res, next) {
	res.render('factorial.jade', { title: 'Factorial' });
});

 

module.exports = router;