const main = (input) => {
  let n = parseInt(input.trim(), 10)
  const alpha = '0abcdefghijklmnopqrstuvwxyz'

  let ans = []

  while (n !== 0) {
    const next = Math.floor(n / 26)
    const r = n % 26
    ans.unshift(alpha[r])
    n = next
  }

  return console.log(ans.join(''))
}

process.env.MYTEST ? test() : main(require('fs').readFileSync('/dev/stdin', 'utf8'))