const main = (input) => {
  let n = BigInt(input.trim())
  const alpha = '0abcdefghijklmnopqrstuvwxyz'
  let ans = []

  while (n !== 0n) {
    if (n === 26n) {
      ans.unshift('z')
      break
    }
    const next = n / 26n
    const r = n % 26n
    ans.unshift(alpha[`${r}`])
    n = next
  }

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

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