using System;
using System.Text.RegularExpressions;
namespace ConsoleApplication_C_Sharp
{
class Program
{
static void Main(string[] args)
{
var s = "c#_c__c++___________java";
s = Regex.Replace(s, "[_]", "[$&]");
Console.WriteLine(s);
}
}
}
/*
run:
c#[_]c[_][_]c++[_][_][_][_][_][_][_][_][_][_][_]java
*/