static void Main(string[] args)
{
do
{
int n;
n = SoNguyen.NhapSoNguyenDuong("Nhap so n:");
Console.Write("\nS(" + n + ")=" + TinhToan.Tong(n));
} while (SoNguyen.NhapSoNguyen("\nTiep tuc (1.Tiep, 0.Khong)") != 0);
}