using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace bt_67
{
class Program
{
static void Main(string[] args)
{
int n,s=0;
do
{
Console.Write("nhap n="); n = int.Parse(Console.ReadLine());
} while (n % 5 != 0 || n <= 0);
for (int i = 1; i <= n; i++)
{
s = s + i;
}
Console.Write("tong la:" + s);
Console.ReadKey();
}
}
}
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace bt_67
{
class Program
{
static void Main(string[] args)
{
int n,s=0;
do
{
Console.Write("nhap n="); n = int.Parse(Console.ReadLine());
} while (n % 5 != 0 || n <= 0);
for (int i = 1; i <= n; i++)
{
s = s + i;
}
Console.Write("tong la:" + s);
Console.ReadKey();
}
}
}