#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;

void rec(ll n, bool isFirst){
    if(n == 0){
        return;
    }

    rec(n / 26, false);
    if(isFirst){
        std::cout << (char)('A' + n % 26);
    }else{
        std::cout << (char)('A' + n % 26 - 1);
    }
}

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

    std::cin >> N;

    if(N == 0){
        std::cout << "A" << std::endl;
    }else{
        rec(N, true);
        std::cout << std::endl;
    }
}