from heapq import *
from collections import Counter
import math

class Solution:
  def rearrangeString(self, str1):
    counts = Counter(str1)
    heap = [
      (-value, char) for char, value in counts.items()
    ]
    heapify(heap)
    if -heap[0][0] > len(str1)//2:
      return ''
    
    res = '_' * len(str1)
    i = 0
    while heap:
      count, char = heappop(heap)
      while count < 0:
        res[i] = char
        i += 2
        if i >= len(res):
          i = 1
        count += 1
    return res