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

int main() {
    LL N;cin>>N;
    if(N<26){
        cout<<(char)('A'+N)<<endl;
        return 0;
    }
    else{
        string s;
        while(N>27){
            s+='A'+N%26;
            N/=26;
        }
        if(N==27)s+="AA";
        else s+='A'+(N-1)%26;
        reverse(s.begin(),s.end());
        cout<<s<<endl;
    }
    return 0;
}