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

const long long MAX = 100000;

int main() {
    string res = "";
    char letter = 'a';
    
    long long N;
    cin >> N;
    while (N > 0) {
        long long low = 0, high = MAX;
        while (high - low > 1) {
            long long x = (low + high) / 2;
            if (x * (x + 1) / 2 <= N) low = x;
            else high = x;
        }
        for (int i = 0; i < low; ++i) res += letter;
        N -= low * (low + 1) / 2;
        ++letter;
    }
    cout << res << endl;
}