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: #include <bits/stdc++.h>
  
  using namespace std;
  using ll =long long;
  
  #define SORT(a) sort((a).begin(),(a).end())
  #define rSORT(a) reverse((a).begin(),(a).end())
  #define For(i, a, b)    for(int i = (a) ; i < (b) ; ++i)
  #define rep(i, n)       For(i, 0, n)
  #define debug(x)  cerr << #x << " = " << (x) << endl;
  template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return true; } return false; }
  template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return true; } return false; }
  void coY() {cout <<"Yes"<<endl;}
  void coN(){cout <<"No"<<endl;}
  
  const ll INF = 1LL << 60;
  
  //Write From this Line
  
  const int mod = 1e9+7;
  int main()
  {
   int n ;
   cin >> n ;
   int ans = 0 ;
  	ans = ( n * (n+1) / 2 );
  	cout << ans << endl;
  }
  
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."}]