//Yukicoder
//Q327 アルファベット列
//




//二次元可変配列
//vector <vector <int>> mass;
//vector <vector <int>> memo;

//#include "stdafx.h"
#include <stdio.h>
#include <iostream>
#include <vector>
#include <list>//list
#include <set> //tree
#include <map> //連想配列
#include <unordered_set> //hash
#include <unordered_map> //hash
#include <algorithm>
#include <iomanip>
#include <string>
#include <stdlib.h>


using namespace std;
typedef unsigned long long ULL;
typedef signed long long SLL;


#define START (0)
#define RIGHT (1)
#define UP    (2)
#define LEFT  (3)
#define DOWN  (4)

#define DATA_MAX (1000000)
#define FMAX(a,b)  ((a)>(b)?(a):(b))
#define FMIX(a,b)  ((a)<(b)?(a):(b))


vector <vector <SLL>> memo2;
vector<SLL> memo1;
vector<SLL> c;
vector<SLL> v;
vector<SLL> dp;

SLL H ,A, B, T;






int main(int argc, char *argv[])
{
	ULL x;
	char s[] = { 'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z' };
	char ans[30];
	//float min = INFINITY;

	cin >> x;

	ULL y, z, keta=0;

		while (1)
		{
			y = x / 26;
			z = x % 26;
			ans[keta] = s[z];

			if (y > 0)
			{
				x = y-1;
				keta++;
			}
			else
			{
				break;
			}
		}
	    

		for (int j = keta; j >= 0; j--)
			cout << ans[j];

	//getchar();
	return 0; //end
}