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

int main(){
    long long N;
    cin >> N;
    string s="ABCDEFGHIJKLMNOPQRSTUVWXYZ";
    if(N<26){
        cout << s[N] << endl;
    }else{
        string ans="";
        int c=(N-26)/26;
        int d=c/26;
        int e=c%26;
        for(int i=0;i<=d;i++){
            ans+=s[e];
        }
        int f=(N-26)%26;
        ans+=s[f];
        cout << ans << endl;
    }
}