#include <iostream>
#include <iomanip>
#include <vector>
#include <algorithm>
#include <numeric>
#include <functional>
#include <cmath>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <sstream>
#include <string>

#define repd(i,a,b) for (int i=(a);i<(b);i++)
#define rep(i,n) repd(i,0,n)
#define var auto
#define mod 1000000007
#define inf 2147483647
#define nil -1
typedef long long ll;

using namespace std;

int inputValue(){
    int a;
    cin >> a;
    return a;
}

template <typename T>
void output(T a, int precision) {
    if(precision > 0){
        cout << fixed << setprecision(precision)  << a << "\n";
    }
    else{
        cout << a << "\n";
    }
}

// end of template

int cal(int n){
    n *= 2;
    double dsqn = sqrt((double)(n));
    return int(dsqn);
}

int isqrt(int n){
    int l = 0;
    int r = n + 1;
    int cnt = 0;
    while(cnt < 50){
        int mid = (l + r) / 2;
        if (mid * mid < n) {
            l = mid;
        }
        else{
            r = mid;
        }
        cnt++;
    }
    return l;
}

int main() {
    cin.tie(0);
    // source code
    string alp = "abcdefghijklmnopqrstuvwxyz";
    
    int N = inputValue();
    
    vector<int> ret(26, 0);
    
    rep(i, 26){
        if (!N) break;
        ret[i] = isqrt(N * 2);
        // output(ret[i], 0);
        N -= ret[i] * (ret[i] + 1) / 2;
    }
    
    rep(i, 26){
        if (!ret[i]) break;
        rep(j, ret[i]){
            cout << alp[i];
        }
    }
    
    cout << endl;
    
    return 0;
}