text: #include <stdio.h>
  #define N 100001
  
  int input[N];
  
  
  int calc(int num)
  {
      if (num ==1)
      {
          return 1;
      }
      return num + calc(num-1);
  }
  
  
  /*
  arr:    -2 1 -3 4 -1 2 1 -5 4
          0  1  2 3 4  5 6  7 8
          6 3 6
          4 -1 2 1
  */
  int main()
  {
      //freopen("/home/lintingbin/test.txt", "r", stdin);
      int n, i, start, end, sum, start_test, end_test, sum_test;
  
      while (scanf("%d", &n) != EOF)
      {
          printf("rv: %d\n", calc(n));
      }
  
  
  
      return 0;
  }