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

using namespace std;

string solve(long long n) {
	string s;
	n++;
	long long len = 1;
	long long len2 = 26;

	while (n > len2) {
		n -= len2;
		len2 *= 26;
		len++;
	}
	n--;

	for (int i = 0; i < len; i++) {
		s += 'A' + n % 26;
		n /= 26;
	}
	reverse(s.begin(), s.end());
	return s;
}

int main() {
	long long n;
	cin >> n;
	cout << solve(n) << endl;

	// for (int i = 0; i <= 26 * 30; i += 26) {
	// 	printf("%5d %3s %3s\n", i, solve(i).c_str(), solve(i-1).c_str());
	// }
	return 0;
}