package main

import (

	"fmt"
)

func main() {
	var N int
	fmt.Scanf("%d", &N)
	fmt.Println(NumToChar(N))
}


func NumToChar(index int) string {
	ans := ""
	if index == 0 {
		return "A"
	}

	for keta := 1; index > 0; keta++ {
		k := (index % 26)
		if keta > 1 {
			k--
		}
		if k == -1 {
			k = 25
			index--
		}
		add := 'A' + k

		ans = string(byte(add)) + ans

		index /= 26


	}
	return ans
}