import Foundation

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

func mainC() {
    var N = readInt()

    var results: [Int] = []

    while N > 0 {
        N -= 1
        results.insert(N % 26, at: 0)
        N /= 26
    }

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

    print(String(name))
}

mainC()