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

using namespace std;

int main() {
	long long n;
	cin >> n;
	std::string result;
	++n;
	while (n > 0) {
		--n;
		char digit = (char)(n % 26LL);
		result.push_back('A' + digit);
		n /= 26;
	}
	std::reverse(result.begin(), result.end());
	cout << result << endl;
	return 0;
}