var N = Int(readLine()!)!
var result = ""
let base = Int(Character("a").unicodeScalars.first!.value)
while N > 0 {
  N -= 1
  let mod = N % 26
  result.append(String(Character(UnicodeScalar(mod + base)!)))
  N /= 26
}
print(String(result.reversed()))