What will be the output of the following C++ code?

#include 
int main ()
{
    FILE * p;
    long size;
    p = fopen ("test.txt", "rb");
    if (p == NULL) 
        perror ("Error opening file");
    else
    {
        fseek (p, 0, SEEK_END); 
        size = ftell (p);
        fclose (p);
        printf (" %ld\n", size);
    }
    return 0;
}