package main

import (
	"fmt"
)

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

func NumToChar(index int) string {
	ans := ""
        
	for ;index >= 0;index-- {
		add := 'A' + (index % 26)
		ans = string(byte(add)) + ans
		index /= 26

	}
	return ans
}