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

using namespace std;

string func(long long n) {
    n++;

    string ret;
    while (n > 0) {
        n--;
        ret = string(1, 'A' + (n % 26)) + ret;
        n /= 26;
    }
    return ret;
}

int main() {
    long long n;
    cin >> n;
    cout << func(n) << endl;
    return 0;
}