#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

int main() {
    long long n;
    cin >> n;

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

    string ret;
    while (n > 26) {
        ret = string(1, 'A' + n % 26) + ret;
        n /= 26;
    }
    ret = string(1, 'A' + n - 1) + ret;

    cout << ret << endl;
    return 0;
}