Lexicographically Maximum Subsequence

You've got string s, consisting of only lowercase English letters. Find its lexicographically maximum subsequence.

We'll call a non-empty string s[p₁p₂... p_k] = s_p1s_p2... s_pk(1 ≤ p₁ < p₂ < ... < p_k ≤ |s|) a subsequence of string s = s₁s₂... s_|s|.

String x = x₁x₂... x_|x| is lexicographically larger than string y = y₁y₂... y_|y|, if either |x| > |y| and x₁ = y₁, x₂ = y₂, ... , x_|y| = y_|y|, or exists such number r (r < |x|, r < |y|), that x₁ = y₁, x₂ = y₂, ... , x_r = y_r and x_r + 1 > y_r + 1. Characters in lines are compared like their ASCII codes.

The single line contains a non-empty string s, consisting only of lowercase English letters. The string's length doesn't exceed 10⁵.

Print the lexicographically maximum subsequence of string s.

ababba

bbba

abbcbccacbbcbaaba

cccccbba

 Note

Let's look at samples and see what the sought subsequences look like (they are marked with uppercase bold letters).
The first sample: aBaBBA
The second sample: abbCbCCaCbbCBaaBA