function log(b, a) {
  return Math.log(a) / Math.log(b)
}

function i2c(n) {
  return String.fromCharCode(97 + n - 1)
}

function main(input) {
  const inputs =input.split('\n')
  const [N] = inputs[0].split(' ').map(Number)
  if (N === 1) {
    console.log('a')
    return
  }
  let digit = Math.ceil(log(26, N))

  // console.log(Math.pow(26, digit - 1))
  const s = i2c(Math.floor(N / Math.pow(26, digit - 1)))
  let name = s
  // console.log(name)
  let r = N % Math.pow(26, digit - 1)
  // console.log(r)
  //
  for(let i = digit - 1; 0 < i; i--) {
    const s = i2c(Math.floor(r / Math.pow(26, i - 1)))
    // console.log(i, s)
    name += s
    r = r % Math.pow(26, i - 1)
  }
  console.log(name)
}

main(require('fs').readFileSync('/dev/stdin', 'utf8').trim())
