def first_non_repeating_character(str1):
  
  char_order = []
  ctr = {}
  for c in str1:
    if c in ctr:
      ctr[c] += 1
    else:
      ctr[c] = 1 
      char_order.append(c)
  for c in char_order:
    if ctr[c] == 1:
      return c
  return None
def heap_queue_largest(nums,n):
  import heapq as hq
  
  largest_nums = hq.nlargest(n, nums)
  return largest_nums