#include <string>
#include <iostream>
#include <cmath>
#include <fstream>
using namespace std;
typedef long long int ll;

int main()
{
	ll n;
	cin >> n;

	if (n == 0) {
		cout << 'A' << endl;
		return 0;
	}

	while (n > 25) {
		cout << (char) (n % 26 + 'A');
		n = n / 26;
	}

	cout << (char)(n % 26 + 'A' -1);


	return 0;
}