using System;
using System.Text.RegularExpressions;
using System.Linq;
 
public class Test
{
	public static void Main()
	{
	    string pattern = @"\bP-?([0-9]+)\b";
	    string s = @"1. G66I11.J270.P5.C90.(+K2H1+)
	    2. G66I11.J90.P-5.(+K2H1+)
	    3. G66I215.4J270.P-55.Q-6.T2531(+K2H1+)";
	    var numbers = Regex.Matches(s, pattern)
	               .Select(i => int.Parse(i.Groups[1].Value))
	               .ToArray();
	    Console.WriteLine("[{0}]", string.Join(", ", numbers));
	}
}

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