using System;
using System.Collections;
using System.Collections.Generic;
using System.Diagnostics;
using System.Diagnostics.CodeAnalysis;
using System.Globalization;
using System.IO;
using System.Linq;
using System.Numerics;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
using System.Text;

namespace AtCoder
{
	class Program
	{
		static void Main()
		{
		}

		delegate T Version2<T>(T arg); // C# 2 Generics
		void Version3() { Version2<int> f = n => n; } // C# 3 Lambda
		interface IVersion4<out T> { } // C# 4 covariance
		async void Version5() { } // C# 5 async/await
		string Version6() { return nameof(Version6); } // C# 6 nameof
		bool Version7() { return int.TryParse("3", out _); } // C# 7 discard
		(int a, int b) Version7_ValueTupe() { return (1, 2); } // C# 7 ValueTuple
		bool Version7_1() { return default; } // C# 7.1 default
		int Version7_2() { return 0x_1; } // C# 7.2 leading digit separator
		void Version7_3<T>() where T : unmanaged { } // C# 7.3 unmanaged generics
		BigInteger SystemNumerics(BigInteger a, BigInteger b) { return a + b; } // System.Numerics.BigInteger
		int Version8() { return true switch { true => 1, false => 0 }; } // C# 8 switch expression
		Span<int> Span(int[] array) { return array.AsSpan(); } // System.Span
		object Version9() { return new(); } // C# 9 target-typed new 
	}
}