OJ Board

During last contest this code get compile error:
-- cut --
Here are the compiler error messages:

g++: 00002138_PC.c: No such file or directory
g++: No input files

-- end --
--
Please say why?
Code:
[cpp]
#include <fstream.h>
#include <math.h>
#include <assert.h>

#define ER 0.000001

const long ...

In problem said: "Within each set, points labels occur in alphabetical order".
Code with sorting this labels gives AC, but without WA.

Maybe BUG or I something not understand?!