package main

import (

	"fmt"
)

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

// 愚直解
func NumToChar(N int) string {
	cur := make([]byte, 1)
	cur[0] = 'A' - 1
	for index := 0; index <= N; index++ {
		cur[len(cur) - 1] += 1
		for j := len(cur) - 1; j >= 0; j-- {
			if cur[j] == 'Z' + 1 {
				cur[j] = 'A'
				if j == 0 {
					tmp := make([]byte, len(cur) + 1)
					tmp[0] = 'A' - 1
					for k := 0; k < len(cur); k++ {
						tmp[1 + k] = cur[k]
					}
					cur = tmp
					j = 1
				}
				cur[j - 1]++
			}
		}
	}
	return string(cur)
}