#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, mod=26;
    while(1){
        ll x;
        x = N%mod;
        lst.push_front(AtoZ[x]);
        N /= mod;
        N--;
        
        //cout << N <<" "<< x << endl;

        if(N==-1) break;
    }

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