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

int main() {
    LL N;cin>>N;

    string _s;
    while(N>=26*27){
        _s+=('A'+(N%26));
        N/=26;
        if(N<26*27&&N>=0){
            N--;
        }
    }
    vector<string> unko;
    string s="AA";
    for(s[0]='A';s[0]<='Z';s[0]++)
    for(s[1]='A';s[1]<='Z';s[1]++)unko.push_back(s);
    s="A";
    for(s[0]='A';s[0]<='Z';s[0]++)unko.push_back(s);
    sort(unko.begin(),unko.end(),
    [](string& x,string& y){
        if(x.size()==y.size())return x<y;
        else return x.size()<y.size();
    });
    reverse(_s.begin(),_s.end());
    if(N>=0)_s=unko[N]+_s;
    cout<<_s<<endl;
    return 0;
}