#include <iostream>
#include <cstdint>
#include <algorithm>

using namespace std;

int main()
{
	cin.tie(nullptr);
	ios::sync_with_stdio(false);

	uint64_t N;
	cin >> N;

	string S;
	while (N >= 26)
		S.push_back('A' + N % 26), N /= 26, --N;

	S.push_back('A' + N % 26);
	reverse(S.begin(), S.end());
	cout << S << '\n';
	return 0;
}