import std.algorithm, std.conv, std.range, std.stdio, std.string; import std.math; // math functions void main() { auto n = readln.chomp.to!int; auto aba = true; while (n > 15) { auto k = n.to!real.sqrt.floor.to!int; if (aba) { foreach (_; 0..k) write("ab"); write("a"); } else { foreach (_; 0..k) write("cd"); write("c"); } n -= k * k; aba = !aba; } writeln("efghijklmnopqrs"[0..n]); }