import std.stdio;

void main() {
	auto s = "abcdefghijklmnopqrstuvwxyz";
	long n;
	readf("%s", &n);
	--n;
	if (n == 0) {
		writeln("a");
		return;
	}

	auto result = new char[0];

	while (n >= 0) {
		result ~= s[n % s.length];
		n /= s.length;
		--n;
	}

	foreach_reverse (e;result) {
		write(e);
	}
	writeln;
}
