output_description: Print the necessary number of candies in total.
  
  * * *
input_description: The input is given from Standard Input in the following format:
  
      
      
      N
attempt: # /usr/bin/python3
  # -*- coding: utf-8 -*-
  from queue import Queue
  from queue import LifoQueue as Stack
  from math import sqrt, floor, ceil, log2
  from fractions import gcd
  from itertools import permutations, combinations
  from operator import itemgetter
  from functools import cmp_to_key
  
  
  __MOD__ = (10**9) + 7
  yn = "YNeos"
  judge = False
  cnt = 0
  ans = None
  
  
  def lcm(a, b):
      return (a * b) // gcd(a, b)
  
  
  def intinput():
      return int(input())
  
  
  def mulinputs():
      return map(int, input().split())
  
  
  def lineinputs(func=intinput):
      datas = []
      while True:
          try:
              datas.append(func())
          except EOFError:
              break
      return datas
  
  
  class ModInt:
      def __init__(self, x):
          self.__x = x % __MOD__
  
      def __add__(self, other):
          if type(other) == int:
              other = self.__class__(other)
              return int(self.__class__((self.__x + other.__x) % __MOD__))
          elif type(other) == ModInt:
              return self.__class__((self.__x + other.__x) % __MOD__)
          else:
              raise Exception("Not Int or Not ModInt")
  
      def __sub__(self, other):
          if type(other) == int:
              other = self.__class__(other)
              return int(self.__class__((self.__x - other.__x) % __MOD__))
          elif type(other) == ModInt:
              return self.__class__((self.__x - other.__x) % __MOD__)
          else:
              raise Exception("Not Int or Not ModInt")
  
      def __mul__(self, other):
          if type(other) == int:
              other = self.__class__(other)
              return int(self.__class__((self.__x * other.__x) % __MOD__))
          elif type(other) == ModInt:
              return self.__class__((self.__x * other.__x) % __MOD__)
          else:
              raise Exception("Not Int or Not ModInt")
  
      def __truediv__(self, other):
          if type(other) == int:
              other = self.__class__(other)
              return int(self.__class__((self.__x * other.__modinv()) % __MOD__))
          elif type(other) == ModInt:
              return self.__class__((self.__x * other.__modinv()) % __MOD__)
          else:
              raise Exception("Not Int or Not ModInt")
  
      def __pow__(self, other):
          if type(other) == int:
              other = self.__class__(other)
              return int(self.__class__(pow(self.__x, other.__x, __MOD__)))
          elif type(other) == ModInt:
              return self.__class__(pow(self.__x, other.__x, __MOD__))
          else:
              raise Exception("Not Int or Not ModInt")
  
      def __modinv(self, m=__MOD__):
          a = self.__x
          if a == 0:
              raise ZeroDivisionError()
          if gcd(a, m) != 1:
              raise Exception("%sの逆数は求まりません。" % a)
          b, u, v = m, 1, 0
          while b != 0:
              t = a // b
              a -= t * b
              a, b = b, a
              u -= t * v
              u, v = v, u
          u %= m
          if u < 0:
              u += m
          return u
  
      def __int__(self):
          return self.__x
  
  
  if __name__ == "__main__":
      N = intinput()
  
      # 出力
      print(N * (1 + N) // 2)
  
  
  # EOF
  
problem_description: Statement
  
  There are N children in AtCoder Kindergarten. Mr. Evi will arrange the
  children in a line, then give 1 candy to the first child in the line, 2
  candies to the second child, ..., N candies to the N-th child. How many
  candies will be necessary in total?
samples: [{"input": "3", "output": "6\n    \n\nThe answer is 1+2+3=6.\n\n* * *"}, {"input": "10", "output": "55\n    \n\nThe sum of the integers from 1 to 10 is 55.\n\n* * *"}, {"input": "1", "output": "1\n    \n\nOnly one child. The answer is 1 in this case."}]