Merkkijono

const readline = require('readline');

const read = readline.createInterface({
	input: process.stdin,
	output: process.stdout,
	terminal: false
})

let str = " ";
let chars = "abcdefghijklmnopqrstuvwxyz";

read.on('line', n => {
	for(i = 0; i < n; i++) {
		for(l = str.length; l > 0; l--) {
			str = str.substr(0, l) + chars[i] + str.substr(l, str.length-l);
		}
	}
	console.log(str);
});

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED

Test 13

Verdict: ACCEPTED

Test 14

Verdict: ACCEPTED

Test 15

Verdict: ACCEPTED

Test 16

Verdict: ACCEPTED