using System;
using System.Text.RegularExpressions;
class Program
{
static String extract_characters_numbers_spaces(String s) {
int len = s.Length;
var regx = new Regex("[a-zA-Z0-9 ]");
String result = "";
for (int i = 0; i < len; i++) {
char ch = s[i];
if (regx.IsMatch(ch.ToString()))
result = result + ch;
}
return result;
}
static void Main() {
String s = "c++$vb.net&%java*() php c# <>/python 3.7.3";
Console.WriteLine(extract_characters_numbers_spaces(s));
}
}
/*
run:
cvbnetjava php c python 373
*/