my both expected output & actual output is same then y test case is wrong

const readline = require("readline");

const inp = readline.createInterface({

input: process.stdin

});

inp.on("line", (data) => {

var str=data.split(" ");

var a = str.toString();

var b =" ";

for(var i=0;i<a.length;i++)

{

b += a.charAt(i)+",";

}

console.log(b.trim());

});