CF339A.Helpful Maths

Xenia the beginner mathematician is a third year student at elementary school. She is now learning the addition operation.

The teacher has written down the sum of multiple numbers. Pupils should calculate the sum. To make the calculation easier, the sum only contains numbers 1, 2 and 3. Still, that isn't enough for Xenia. She is only beginning to count, so she can calculate a sum only if the summands follow in non-decreasing order. For example, she can't calculate sum 1+3+2+1 but she can calculate sums 1+1+2 and 3+3.

You've got the sum that was written on the board. Rearrange the summans and print the sum in such a way that Xenia can calculate the sum.

初学数学的 Xenia 是小学三年级的学生，她正在学习加法运算。

老师在黑板上写下了多个数的和，学生们需要计算这个和。为了简化计算，该和式中只包含数字 1、2 和 3。但即便如此，对 Xenia 来说仍不够简单：她刚开始学习计数，因此只有当加数按非递减顺序排列时，她才能正确计算该和。例如，她无法计算 $1+3+2+1$，但可以计算 $1+1+2$ 和 $3+3$。

你得到了黑板上所写的和式。请重新排列其中的加数，并以 Xenia 能够计算的形式（即加数按非递减顺序排列）输出该和式。

The first line contains a non-empty string s — the sum Xenia needs to count. String s contains no spaces. It only contains digits and characters "+". Besides, string s is a correct sum of numbers 1, 2 and 3. String s is at most 100 characters long.

第一行包含一个非空字符串 $s$ — Xenia 需要求和的表达式。字符串 $s$ 中不包含空格，仅包含数字和字符 +。此外，字符串 $s$ 是由数字 1、2 和 3 构成的合法加法表达式。字符串 $s$ 的长度最多为 100 个字符。

Print the new sum that Xenia can count.

输出 Xenia 能够计算出的新总和。