import Foundation
//
//infix operator ...
//extension String{
//    static func ...(left: String, right: String) ->Array<Character> {
//        return ((left.unicodeScalars.first!.value) ... (right.unicodeScalars.first!.value)).map { Character(UnicodeScalar($0)!) }
//    }
//}

func main() {

    var n = Int(readLine()!)!
    var amari = n%26
    let alph = ["a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z"]
    var ans = String()
    while amari != 0 && n >= 26{
        ans = String((alph[n%26-1])) + ans
        n = n/26
        amari = n%26
    }
    if n%26 == 0 {
        let counter = n/26
        for _ in 1...counter{
            ans = String((alph[0])) + ans
        }
    }
    else{
        ans = String((alph[amari-1])) + ans
    }

    print(ans)
}

main()
