#include <iostream>
#include <cstdio>
#include <string>
#include <algorithm>

using namespace std;

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

	string s;
	if (n == 0) {
		s = "A";
	} else {
		while (n > 0) {
			s += 'A' + n % 26 - 1;
			n /= 26;
		}
		s[0]++;
		reverse(s.begin(), s.end());
	}
	cout << s << endl;
}