import std;
void main () {
	long n, p;
	while (readf !(" %s") (n) > 0) {
		for (p = 26, n -= 1; p <= n; p *= 26) {
			n -= p;
		}
		for (p /= 26; p > 0; n %= p, p /= 26) {
			write (cast (char) (n / p + 'a'));
		}
		writeln;
	}
}
