using System;
using System.Linq;

public class Test
{
	
	public static string Extract(string str, string keyword)
    {

        string[] arr = str.Split('.');
        string answer = string.Empty;

        foreach(string sentence in arr)
        {
            if(sentence.Split(' ').Any(w => w == keyword))
                    answer += sentence+". ";
        }

        return answer;
    }
	
	public static void Main()
	{
		string example = "We are living in a yellow submarine. We don't have anything else. Inside the submarine is very tight. So we are drinking all the day. We will move out of it in 5 days.";

string keyword = "in";
string answer = Extract(example, keyword);
Console.WriteLine(answer);
	}
}