package main

import "fmt"

func main() {
	ans := make([]byte, 0)
	var N int
	fmt.Scan(&N)
	N++
	for N > 0 {
		N--
		ans = append(ans, byte(N%26+'A'))
		N /= 26
	}
	for i := 0; i < len(ans)/2; i++ {
		ans[i], ans[len(ans)-i-1] = ans[len(ans)-i-1], ans[i]
	}
	fmt.Println(string(ans))
}