import Foundation

var n = Int(readLine()!)!

var a = 0
let b = n % 26

var c = [Int]()

while n >= 26 {
    c += [n % 26]
    n /= 26
}

c += [n % 26]

print(String(c.reversed().map{ Character(UnicodeScalar($0 + 96)!) }))
