#include <iostream>
#include <string>
#include <algorithm>
using namespace std;

int main() {
    // ???1e12?????
    long long n;
    cin >> n;
    
    string res;
    while (true) {
        // ?????1??????? 0-25
        n--;
        // ??????????
        int remainder = n % 26;
        // ???????
        res += (char)('A' + remainder);
        // ??26?????
        n = n / 26;
        // n?0?????
        if (n == 0) break;
    }
    
    // ?????????????????
    reverse(res.begin(), res.end());
    cout << res << endl;
    
    return 0;
}