// #pragma GCC optimize ("Ofast")
// #pragma GCC optimize ("unroll-loops")
// #pragma GCC target ("avx,avx2,fma")
#include <bits/stdc++.h>

using std::cin, std::cout, std::cerr;
using ll = long long;

ll Pow(ll a, ll b) {
    ll r = 1;
    while(b) {
        r *= a;
        b --;
    }
    return r;
}

int main() {
    std::ios::sync_with_stdio(false);
    ll n; cin >> n;
    std::string s = "";
    int d = 1;
    while(n >= Pow(26, d)) {
        n -= Pow(26, d);
        d ++;
    }
    
    for(int i = d - 1; i >= 0; i --) {
        char c = 'A';
        while(n >= Pow(26, i)) {
            n -= Pow(26, i);
            c ++;
        }
        s += c;
    }
    cout << s << '\n';
}