var input = Int(readLine()!)!

var result: [Int] = []

while input > 0 {
  if input % 26 == 0 {
    result.append(26)
  } else {
	result.append(input % 26)
  }
  input /= 26
}
let base = Int(Character("a").unicodeScalars.first!.value)
print(result.map{ String(Character(UnicodeScalar($0 + base - 1)!))}.reversed().joined())
