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

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