Can’t read value of POST

I can’t get the values from a simple form. It has 2 files: APP.js and FORM.ejs. I am trying to receive the values from the form.

APP.js:

const http = require('http');
const express = require("express");
const S1_APP = express();
const ejs = require("ejs"); 
const bodyParser = require("body-parser"); 
S1_APP.use(bodyParser.urlencoded({ extended: false }));
S1_APP.set('view engine', 'ejs');//template engine

S1_APP.get("", function (req, res) {
    res.render('FORM.ejs');  
});

S1_APP.post("/",function(req, res) {

// here I need to read the value (myvalue 1 or 2) 
// that is send via the form in FORM.ejs
// I have tried req.body, that is empty
// I have tried req.value, that is undefined

});
S1_APP.listen(8080, function (err) {
    if (err) console.log(err);
    console.log("Server listening on PORT 8080");
});

FORM.ejs:

<html lang="en" >
<head><meta charset="utf-8"><meta http-equiv="X-UA-Compatible" content="IE=edge"></head>

<body>
    <form method="POST" action="/">
        <button type="submit" value="myvalue1"  >POST 1</button>
        <button type="submit" value="myvalue2"  >POST 2</button>
    </form>
</body>
</html>