import Foundation

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

func mainC() {
    var N = readInt()

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

    (0...9).forEach { index in
        pows.append(pows[index] * 26)
    }

    var numbers = pows

    (1...9).forEach { index in
        numbers[index] = numbers[index - 1] + numbers[index]
    }

    pows.enumerated().reversed().forEach { (index, element) in
        if numbers[index] <= N {
            let result = N / element
            if result > 26 {
                results.append(26)
                N %= element
                N += (result - 26) * element
            } else {
                results.append(result)
                N %= element
            }
        }
    }

    if N != 0 {
        results.append(N)
    }

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

    print(String(name))
}

mainC()