void DuyetCacPhanTuTrenDuongCheoChinh(int a[][MAX], int n)
{
	for(int i = 0; i < n; i++)
	{
		printf("%4d",a[i][i]);
	}
	
}

Line 1: error: 'MAX' undeclared here (not in a function)
In function 'DuyetCacPhanTuTrenDuongCheoChinh':
Line 3: error: 'for' loop initial declaration used outside C99 mode