package main

import (
	"bufio"
	"bytes"
	"fmt"
	"os"
	"strconv"
)

var sc = bufio.NewScanner(os.Stdin)
var rdr = bufio.NewReaderSize(os.Stdin, 1000000)

func main() {
	sc.Split(bufio.ScanWords)
	// n := nextInt()
	n := 675
	n++
	offset := 1
	c := 0
	for ; n >= offset; c++ {
		n -= offset
		offset *= 26
	}

	s := bytes.Repeat([]byte{'A'}, c)
	for i := c - 1; n >= 26; i, n = i-1, n/26 {
		s[i] += byte(n % 26)
	}
	s[0] += byte(n)

	fmt.Println(string(s))
}

func nextLine() string {
	sc.Scan()
	return sc.Text()
}

func nextInt() int {
	i, _ := strconv.Atoi(nextLine())
	return i
}

func nextInt64() int64 {
	i, _ := strconv.ParseInt(nextLine(), 10, 64)
	return i
}

func nextUint64() uint64 {
	i, _ := strconv.ParseUint(nextLine(), 10, 64)
	return i
}

func nextFloat() float64 {
	f, _ := strconv.ParseFloat(nextLine(), 64)
	return f
}

func readLine() string {
	buf := make([]byte, 0, 1000000)
	for {
		l, p, e := rdr.ReadLine()
		if e != nil {
			panic(e)
		}
		buf = append(buf, l...)
		if !p {
			break
		}
	}
	return string(buf)
}