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

using namespace std;

int main() {
    long long n;
    cin >> n;
    if (n < 26) {
        cout << (char) ('A' + n) << endl;
        return 0;
    }

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

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