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

using namespace std;

int main() {
    long long N;
    cin >> N;
    
    string result = "";
    
    // ?????N=0 ????? "A"
    if (N == 0) {
        cout << "A" << endl;
        return 0;
    }
    // ???????
    while (N > 0) {
        // ???????0??A?1??B?...?25??Z?
        result += char('A' + (N % 26));
        // ???????1??????????"?"
        N = N / 26;
    }
    
    // ?????????????????
    reverse(result.begin(), result.end());
    
    cout << result << endl;
    return 0;
}