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

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