output_description: Print the maximum total number of ingredients that Snuke's N servings of
  Skewer Meal can hold.
  
  * * *
input_description: The input is given from Standard Input in the following format:
  
      
      
      N
      L_1 L_2 ... L_{2N}
attempt: import math
  
  
  def getInt():
      return int(input())
  
  
  def getIntList():
      return [int(x) for x in input().split()]
  
  
  def zeros(n):
      return [0] * n
  
  
  def zeros2(n, m):
      return [zeros(m) for i in range(n)]  # obsoleted zeros((n, m))で代替
  
  
  class Debug:
      def __init__(self):
          self.debug = True
  
      def off(self):
          self.debug = False
  
      def dmp(self, x, cmt=""):
          if self.debug:
              if cmt != "":
                  w = cmt + ": " + str(x)
              else:
                  w = str(x)
              print(w)
          return x
  
  
  def prob():  # WA 2
      d = Debug()
      d.off()
      N = getInt()
      d.dmp((N), "N")
      L = getIntList()
      d.dmp((L), "L")
      L.sort()
      count = 0
      for i in range(N):
          count += min(L[i * 2], L[i * 2 + 1])
      return count
  
  
  ans = prob()
  print(ans)
  
problem_description: Statement
  
  Snuke is having a barbeque party.
  
  At the party, he will make N servings of _Skewer Meal_.
  
  ![](https://agc001.contest.atcoder.jp/img/agc/001/Gg9pvPKw/abbq.png)
  
  Example of a serving of Skewer Meal
  
  He has a stock of 2N skewers, all of which will be used in Skewer Meal. The
  length of the i-th skewer is L_i. Also, he has an infinite supply of
  ingredients.
  
  To make a serving of Skewer Meal, he picks 2 skewers and threads ingredients
  onto those skewers. Let the length of the shorter skewer be x, then the
  serving can hold the maximum of x ingredients.
  
  What is the maximum total number of ingredients that his N servings of Skewer
  Meal can hold, if he uses the skewers optimally?
samples: [{"input": "2\n    1 3 1 2", "output": "3\n    \n\nIf he makes a serving using the first and third skewers, and another using the\nsecond and fourth skewers, each serving will hold 1 and 2 ingredients, for the\ntotal of 3.\n\n* * *"}, {"input": "5\n    100 1 2 3 14 15 58 58 58 29", "output": "135"}]