const { isNumber } = require("util")

const input = require("fs").readFileSync("/dev/stdin", "utf8")
let cin = input.split(/ |\n/), cid = 0
const next = () => cin[cid++]
const nexts = (n) => cin.slice(cid, cid+=n).map(i=>parseInt(i))

const alphabet = [
    'a',
    'b',
    'c',
    'd',
    'e',
    'f',
    'g',
    'h',
    'i',
    'j',
    'k',
    'l',
    'm',
    'n',
    'o',
    'p',
    'q',
    'r',
    's',
    't',
    'u',
    'v',
    'w',
    'x',
    'y',
    'z'
]

let n = parseInt(next()) - 1
result = ''
while (n > 0) {
    result = alphabet[n%26] + result
    n = Math.floor(n/26) - 1
}
if (n === 0) {
    console.log("a" + result)
} else {
    console.log(result)
}
