C:\Lang\dotnet\sdk\6.0.401\Sdks\Microsoft.NET.Sdk\targets\Microsoft.NET.Sdk.DefaultItems.targets(134,5): warning NETSDK1182: Targeting .NET 6.0 or higher in Visual Studio 2019 is not supported. [D:\cats-judge\run\csharp.csproj]
D:\cats-judge\run\7145058.cs(9,35): error CS0246: The type or namespace name 'StreamReader' could not be found (are you missing a using directive or an assembly reference?) [D:\cats-judge\run\csharp.csproj]
D:\cats-judge\run\7145058.cs(14,16): error CS0246: The type or namespace name 'StreamWriter' could not be found (are you missing a using directive or an assembly reference?) [D:\cats-judge\run\csharp.csproj]
D:\cats-judge\run\7145058.cs(14,46): error CS0246: The type or namespace name 'StreamWriter' could not be found (are you missing a using directive or an assembly reference?) [D:\cats-judge\run\csharp.csproj]