using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text.RegularExpressions;

public class Test
{
	public static void Main()
	{
		var text = "ما المجموع:\n1+2";
    	var result = Regex.Match(text, @"المجموع:\s*(.+)")?.Groups[1].Value;
        Console.WriteLine(result);
	}
}