void AverSumofEveryStudent(STU stu[], int n, int m)
{
	int i, j;
	for (i=0; i<n; i++)
	{
	    stu[i].sum = 0;
	    for (j=0; j<m; j++)
	    {
            stu[i].sum = stu[i].sum + stu[i].score[j];
	    }
	    stu[i].aver = m>0 ? stu[i].sum / m : -1;
	    printf("student %d: sum = %.0f, aver = %.0f\n", 
i+1, stu[i].sum, stu[i].aver);
	}	
}