using System;
using System.Text.RegularExpressions;
public class Example
{
public static void Main()
{
string str = "Hello.world. This..is a test.\nso yeah...";
Console.WriteLine(new Regex(@"(.)\.([^\s\.])").Replace(str, "${1}. ${2}"));
}
}
dXNpbmcgU3lzdGVtOwp1c2luZyBTeXN0ZW0uVGV4dC5SZWd1bGFyRXhwcmVzc2lvbnM7CgpwdWJsaWMgY2xhc3MgRXhhbXBsZQp7CiAgIHB1YmxpYyBzdGF0aWMgdm9pZCBNYWluKCkKICAgewogICAgICBzdHJpbmcgc3RyID0gIkhlbGxvLndvcmxkLiBUaGlzLi5pcyBhIHRlc3QuXG5zbyB5ZWFoLi4uIjsKICAgICAgQ29uc29sZS5Xcml0ZUxpbmUobmV3IFJlZ2V4KEAiKC4pXC4oW15cc1wuXSkiKS5SZXBsYWNlKHN0ciwgIiR7MX0uICR7Mn0iKSk7ICAgICAgICAgICAgICAgICAgICAgICAgICAgICAKICAgfQp9