class Proc {
    public func doProc() {
        let num = Int64(readLine()!)!

        let ans = getAns(num, true)

        if ans.count == 0 {
            print("A")
        } else {
            print(ans)
        }
    }

    private func getAns(_ num:Int64, _ fst:Bool)->String {
        if num == 0 {
            return ""
        }

        let ch = "ABCDEFGHIJKLMNOPQRSTUVWXYZ".map{ $0 }

        var sub:Int64
        if num > 26 || fst {
            sub = num % 26
            var ans = getAns((num - sub) / 26, false)
            ans.append(ch[Int(sub)])
            return ans
        } else {
            sub = num - 1
            return String(ch[Int(sub)])
        }
    }

}

Proc().doProc()