import Foundation

func readInt() -> Int {
    return Int(readLine()!)!
}

func mainC() {
    var N = readInt()

    var pows = [26]
    var results: [Int] = []

    // 26の0, 1, 2, 3, 4...9錠を求める
    (0...9).forEach { index in
        pows.append(pows[index] * 26)
    }

    pows.reversed().forEach { pow in
        if pow < N {
            results.append(N / pow)
            N %= pow
        }
    }

    results.append(N)

    let name = results.map { offset in
        return Character(UnicodeScalar(Int(Character("a").unicodeScalars.first!.value) + offset - 1)!)
    }

    print(String(name))
}

mainC()