#include <bits/stdc++.h>

using namespace std;

#define fst(t) std::get<0>(t)
#define snd(t) std::get<1>(t)
#define thd(t) std::get<2>(t)
#define unless(p) if(!(p))
#define until(p) while(!(p))

using ll = long long;
using P = std::tuple<int,int>;

const int dx[8] = {-1, 1, 0, 0, -1, -1, 1, 1}, dy[8] = {0, 0, -1, 1, -1, 1, -1, 1};

ll N;
vector<char> v;

int main(){
    std::cin.tie(nullptr);
    std::ios::sync_with_stdio(false);

    std::cin >> N;

    if(N == 0){
        std::cout << "A" << std::endl;
        return 0;
    }
    
    while(N > 0){
        v.emplace_back((char)('A' + N % 26));
        N /= 26;
        --N;
    }

    reverse(v.begin(), v.end());
    for(const auto &c : v){
        std::cout << c;
    }
    std::cout << std::endl;
}