#include <bits/stdc++.h>
using namespace std;
using ll = long long;

int main(){
    ll n;
    cin >> n;
    string s;
    if(n == 0)s += 'A';
    while(n){
        if(s.size())n--;
        s += n % 26 + 'A';
        n /= 26;
    }
    reverse(s.begin(), s.end());
    cout << s << '\n';
}