Couples Frequency

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

class UserLogs
{
    static void Main()
    {
        string input = Console.ReadLine();
        string pattern = @"\s+";
        string[] substrings = Regex.Split(input, pattern);

        Dictionary<string, int> combinations = new Dictionary<string, int>();
        for (int i = 0; i < substrings.Length - 1; i++)
        {
            if (combinations.ContainsKey(substrings[i] + " " + substrings[i + 1]))
            {
                int currentValue = combinations[substrings[i] + " " + substrings[i + 1]];
                combinations[substrings[i] + " " + substrings[i + 1]] = currentValue + 1;
            }
            else
            {
                combinations.Add(substrings[i] + " " + substrings[i + 1], 1);
            }
        }

        int total = 0;

        foreach (var item in combinations)
        {
            total += item.Value;
        }

        foreach (var item in combinations)
        {
            Console.WriteLine("{0} -> {1:F2}%", item.Key, ((double)item.Value / (double)total) * 100);
        }
    }
}