#include <iostream>
#include <cmath>
#include <list>

using namespace std;

typedef unsigned long long uint64;

int main() {
    const char alp[] =
      {'A','B','C','D','E','F','G','H','I','J','K','L','M',
       'N','O','P','Q','R','S','T','U','V','W','X','Y','Z'};
    uint64 dec;
    int digits;
    list<char> out;

    cin >> dec;

    if (dec < 26) {
        out.push_front(alp[dec % 26]);
    } else {
        for (digits = 1; dec >= 26 * ((uint64) pow(26, digits) - 1) / 25; digits++);
        do {
            if (digits == 1) {
                out.push_front(alp[dec % 27 - 1]);
            } else {
                out.push_front(alp[dec % 26]);
            }
            dec /= 26;
        } while (--digits > 0);
    }

    list<char>::iterator it = out.begin();
    while (it != out.end()) {
      cout << *it;
      ++it;
    }
    cout << endl;

    return 0;
}