//ritik_patel05

//&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& STL DEBUGGER &&&&&&&&&&&&&&&&&&&&&&&&&&&

// #define _GLIBCXX_DEBUG       // Iterator safety; out-of-bounds access for Containers, etc.
// #pragma GCC optimize "trapv" // abort() on (signed) integer overflow.

//&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& LIBRARIES &&&&&&&&&&&&&&&&&&&&&&&&&&&

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

/*#include <ext/pb_ds/assoc_container.hpp> // Common file
#include <ext/pb_ds/tree_policy.hpp> // Including tree_order_statistics_node_update
template<typename T, typename V = __gnu_pbds::null_type>
using ordered_set = __gnu_pbds::tree<T, V, less<T>, __gnu_pbds::rb_tree_tag, __gnu_pbds::tree_order_statistics_node_update>; 
*/
//find_by_order()->returns an iterator to the k-th largest element(0-based indexing)
//order_of_key()->Number of items that are strictly smaller than our item

//&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& DEFINES &&&&&&&&&&&&&&&&&&&&&&&&&&&

#define int long long int
#define all(i) i.begin(), i.end()
#define sz(a) (int)a.size()
 
// const ld PI  = 3.141592;
const int dx4[4] = {0, 1, 0, -1};
const int dy4[4] = {-1, 0, 1, 0};
const int dx8[8] = {-1, -1, -1, 0, 1, 1, 1, 0};
const int dy8[8] = {-1, 0, 1, 1, 1, 0, -1, -1};
 
//&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& DEBUG &&&&&&&&&&&&&&&&&&&&&&&&&&&
 
#define XOX
vector<string> vec_splitter(string s) {
    for(char& c: s) c = c == ','?  ' ': c;
    stringstream ss; ss << s;
    vector<string> res;
    for(string z; ss >> z; res.push_back(z));
    return res;
}
 
void debug_out(vector<string> __attribute__ ((unused)) args, __attribute__ ((unused)) int idx) { cerr << endl; }
template <typename Head, typename... Tail>
void debug_out(vector<string> args, int idx, Head H, Tail... T) {
    if(idx > 0) cerr << ", ";
    stringstream ss; ss << H;
    cerr << args[idx] << " = " << ss.str();
    debug_out(args, idx + 1, T...);
}
 
#ifdef XOX
#define debug(...) debug_out(vec_splitter(#__VA_ARGS__), 0, __VA_ARGS__)
#else
#define debug(...) 42
#endif
 
 
//&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& CODE &&&&&&&&&&&&&&&&&&&&&&&&&&&

int fast_power(int a, int b){
    int res = 1;
    while(b){
        if(b&1) res *= a;
        a *= a;
        b >>= 1;
    }
    return res;
}

void solve(){
    int n; cin >> n;
    int before = 0;
    for(int len = 1; ; ++len){
        int total = fast_power((int)26, len);
        if(n <= total + before){
            int covered = before;
            string ans = "";
            for(int j = 1; j <= len; ++j){
                for(char ch = 'a'; ch <= 'z'; ++ch){
                    int its_count = fast_power((int)26, (len - j));
                    debug(len, ch, covered, its_count, n, ans);
                    if(covered + its_count < n){
                        covered += its_count;
                    } else {
                        ans += ch;
                        break;
                    }
                }
            }
            cout << ans << '\n';
            return;
        }
        before += total;
    }

}


int32_t main(){
    ios_base::sync_with_stdio(false);cin.tie(nullptr);cout.tie(nullptr); 
    int T = 1; 
    // cin >> T;
    for(int i = 1; i <= T; ++i){
        // brute();
        solve();
    }
    return 0;
}

/*
Sample inp
*/


Measured memory_bytes: 3672