URAL1068[Sum]

水题，不说。

CODE:

/*

PROGRAM: $PROGRAM

AUTHOR: Su Jiao

DATE: 2010-4-3

DESCRIPTION:

$DESCRIPTION

*/

#include <iostream>

using std::cin;

using std::cout;

#include <fstream>

using std::ifstream;

using std::ofstream;

#include <sstream>

using std::stringstream;

using std::endl;

#include <vector>

using std::vector;

#include <string>

using std::string;

#include <stack>

using std::stack;

#include <queue>

using std::queue;

#include <set>

using std::set;

#include <map>

using std::map;

using std::pair;

using std::make_pair;

#include <algorithm>

using std::sort;

#include <cassert>

//using std::assert;

 

class Application

{

      int N;

      static int abs(int a)

      {

             return a>0?a:-a;

      }

      public:

      Application()

      {

                   cin>>N;

      }

      int run()

      {

          cout<<(N+1)*(abs(N-1)+1)/2<<endl;

          return 0;

      }

};

 

int main()

{

    Application app;

    return app.run();

}