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

typedef long long ll;

string AtoZ;

int main() {
    ll N;
    cin >> N;
    list<char> lst;
    for(char ch='A'; ch<='Z'; ch++){
        AtoZ.push_back(ch);
    }
    ll cnt=0;
    while(1){
        ll x;
        x = N%26;
        N /= 26;
        if(cnt++==0) lst.push_front(AtoZ[x]);
        else lst.push_front(AtoZ[x-1]);
        //cout << N <<" "<< x << endl;
        if(N==1){
            lst.push_front('A');
            break;
        }
        if(N==0) break;
    }

    for(auto itr=lst.begin(); itr!=lst.end(); itr++){
        cout << *itr;
    }
    cout << endl;
}