#include<bits/stdc++.h>
using namespace std;
using ll = long long;

template<class T>bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }

#define FOR(i,a,b) for(ll i=(a);i<(b);++i)
#define ALL(v) (v).begin(), (v).end()
#define p(s) cout<<(s)<<endl
#define p2(s, t) cout << (s) << " " << (t) << endl
#define br() p("")
#define pn(s) cout << (#s) << " " << (s) << endl

string encode26(ll v, ll keta){
    vector<ll> A;
    FOR(i, 0, keta){
        A.push_back(v%26);
        v /= 26;
    }
    reverse(ALL(A));
    stringstream ss;
    for(ll a : A){
        char c = a + 'A';
        ss << c;
    }
    return ss.str();
}

ll ll_pow(ll a, ll n){
    ll ans = 1;
    FOR(i, 0, n){
        ans *= a;
    }
    return ans;
}

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

    // input
    ll N;
    cin >> N;

    if(N<=25){
        char c = 'A' + N;
        p(c);
        return 0;
    }

    ll keta;
    FOR(i, 1, 100){
        if(N >= ll_pow(26, i)){
            N -= ll_pow(26, i);
        }else{
            keta = i;
            break;
        }
    }

    auto s = encode26(N, keta);
    p(s);
    
    return 0;
}