#include <iostream>
#include <fstream>
#include <vector>
#include <cstring>
#include <string>
#include <algorithm>
#include <iomanip>
using namespace std;
typedef long long ll;

int main() {
	cin.tie(0);
	ios::sync_with_stdio(false);

	ll N;
	cin >> N;

	ll M = 26;
	while(N >= M) {
		if(N % M == 0) {
			while(M) {
				cout << 'A';
				M /= 26;
			}
			cout << 'A' << endl;
			return 0;
		}
		M *= 26;
	}

	if(N == 0) {
		cout << "A" << endl;
		return 0;
	}

	string ans;
	while(N) {
		ans = char('A' + (N % 26)) + ans;
		N /= 26;
	}

	cout << ans << endl;
}