//https://ncode.syosetu.com/n4830bu/254/
#include <bits/stdc++.h>
using namespace std;

int main() {
    int N;
    cin >> N;
    string ans;
    char c = 'a';
    for (long long len = 1e5; len >= 1; len--) {
        long long maine = len * (len + 1) / 2;
        if (N >= maine) {
            N -= maine;
            for (int i = 0; i < len; i++) {
                ans += c;
            }
            c++;
            len++;
        }
    }
    cout << ans << endl;
}