"use strict";

function Main(input) {
    // 1行目がinput[0], 2行目がinput[1], …に入る
    input = input.split("\n");
    let n = parseInt(input[0], 10);

    //出力
    console.log(to(n).toLowerCase());
}

function to(num) {
    const mod = num % 26;
    let pow = num / 26 | 0;
    const out = mod ? String.fromCharCode(64 + mod) : (--pow, 'z');

    return pow ? to(pow) + out : out;
}

Main(require("fs").readFileSync("/dev/stdin", "utf8"));