>>870175

>дотнетмарази подъехали

[code='c#']
using System;

namespace TRC
{
class Program
{
static void Main(string[] args)
{
while (true)
{
Console.WriteLine("Enter a number.");
string line = Console.ReadLine();
int n;

if (!int.TryParse(line, out n))
{
Console.WriteLine("That wasn't a number");
continue;
}

if (n < 0)
{
Console.WriteLine("The number must be a positive integer.");
continue;
}

int res = n * (n + 1) / 2;

Console.WriteLine($"Triangle number is {res}");
}
}
}
}
[/code]