import std.stdio, std.array, std.string, std.conv, std.algorithm;
import std.typecons, std.range, std.random, std.math, std.container;
import std.numeric, std.bigint, core.bitop;


void main() {
    auto N = readln.chomp.to!int;

    if (N == 0) {
        "a".writeln;
        return;
    }

    string ans = "";
    char c = 'a';

    while (N > 0) {
        ans ~= c;
        int tmp = 1;
        while (N - tmp >= 0) {
            N -= tmp;
            ans ~= c;
            tmp += 1;
        }
        c += 1;
    }

    ans.writeln;
}
