Language: C

using System;
using System.Collections.Generic;
using System.Windows;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Atcoder
{
    public class Program
    {
        static void Main(string[] args)
        {
            var n = Read();
            for (int i = 0; i < n.Length; i++)
            {
                if (n[i] == '7')
                {
                    WriteRead("Yes");
                    break;
                }
            }
            WriteRead("No");
        }

        public static string Read()
        {
            return Console.ReadLine();
        }

        public static string[] ReadSplit()
        {
            return Console.ReadLine().Split(' ');
        }

        public static void WriteRead(object str)
        {
            Console.WriteLine(str);
            Read();
        }

        public static void Write(object str)
        {
            Console.WriteLine(str);
        }
    }
}


public static class Extentions
{
    public static int ToInt(this object obj)
    {
        return int.Parse(obj.ToString());
    }

    public static decimal ToDecimal(this object obj)
    {
        return decimal.Parse(obj.ToString());
    }

    public static double ToDouble(this object obj)
    {
        return double.Parse(obj.ToString());
    }

    public static T2 GetValueZero<T1, T2>(this Dictionary<T1, T2> d, T1 key) where T2 : struct
    {
        T2 value;
        if (d.TryGetValue(key, out value))
        {
            return value;
        }
        return new T2();
    }
}



Compiler output:
main.c:1:1: error: unknown type name 'using'
    1 | using System;
      | ^~~~~
main.c:2:1: error: unknown type name 'using'
    2 | using System.Collections.Generic;
      | ^~~~~
main.c:2:13: error: expected '=', ',', ';', 'asm' or '__attribute__' before '.' token
    2 | using System.Collections.Generic;
      |             ^
main.c:3:1: error: unknown type name 'using'
    3 | using System.Windows;
      | ^~~~~
main.c:3:13: error: expected '=', ',', ';', 'asm' or '__attribute__' before '.' token
    3 | using System.Windows;
      |             ^
main.c:4:1: error: unknown type name 'using'
    4 | using System.Linq;
      | ^~~~~
main.c:4:13: error: expected '=', ',', ';', 'asm' or '__attribute__' before '.' token
    4 | using System.Linq;
      |             ^
main.c:5:1: error: unknown type name 'using'
    5 | using System.Text;
      | ^~~~~
main.c:5:13: error: expected '=', ',', ';', 'asm' or '__attribute__' before '.' token
    5 | using System.Text;
      |             ^
main.c:6:1: error: unknown type name 'using'
    6 | using System.Threading.Tasks;
      | ^~~~~
main.c:6:13: error: expected '=', ',', ';', 'asm' or '__attribute__' before '.' token
    6 | using System.Threading.Tasks;
      |             ^
main.c:8:1: error: unknown type name 'namespace'
    8 | namespace Atcoder
      | ^~~~~~~~~
main.c:9:1: error: expected '=', ',', ';', 'asm' or '__attribute__' before '{' token
    9 | {
      | ^
main.c:50:7: error: expected ';' before 'static'
   50 | public static class Extentions
      |       ^~~~~~~
      |       ;
main.c:50:15: error: unknown type name 'class'
   50 | public static class Extentions
      |               ^~~~~
main.c:51:1: error: expected '=', ',', ';', 'asm' or '__attribute__' before '{' token
   51 | {
      | ^