#include <iostream>
#include <vector>

using ll = long long int;

int main(){
    std::ios::sync_with_stdio(false);
    std::cin.tie(0);

    ll n;
    std::vector<char> str;
    std::cin >> n;

    do{
        str.push_back(n%26+'A');
        n/=26;
        --n;
    }while(n!=-1);

    for(auto rit=str.rbegin(); rit!=str.rend(); ++rit){
        std::cout << *rit;
    }
    std::cout << "\n";

    return 0;
}