#include <bits/stdc++.h>
using namespace std;

int main() {
    long long N;
    cin >> N;
    N--;
    string s;
    while (N >= 0) {
        s.insert(s.begin(), 'a' + (N % 26));
        N = N / 26 - 1;
    }
    cout << s << endl;
}