what's wrong in my code:
#include <stdio.h>

main()
{
      int a;
      scanf("%d",&a);
      if( a >= 0 )
          printf("%d",a*(a+1)/2);
      else
      {
          a = -a;
          printf("-%d",a*(a+1)/2-1);
      }
      return 0;
}

Edited by author 25.08.2012 15:05

Edited by author 25.08.2012 15:06

If a is 0,the answer IS 1, not 0.