using System.CodeDom.Compiler;

using System.Collections.Generic;

using System.Collections;

using System.ComponentModel;

using System.Diagnostics.CodeAnalysis;

using System.Globalization;

using System.IO;

using System.Linq;

using System.Reflection;

using System.Runtime.Serialization;

using System.Text.RegularExpressions;

using System.Text;

using System;

​

class Program

{

​

​

​

    // Complete the prims function below.

    static int prims(int n, int[][] edges, int start)

    {

        HashSet<int> usedNodes = new HashSet<int>();

        usedNodes.Add(start);

        var sortedEdges = edges.OrderBy(p => p[2]).ToArray();

        int numberOfEdges = 0;

        int sum = 0;

        for (int i = 0; i < sortedEdges.Count(); i++)

        {

            if (numberOfEdges == n - 1) return sum;

            if (sortedEdges[i] == null) continue;

            int numberOfExists = 0;

            if (usedNodes.Contains(sortedEdges[i][0])) numberOfExists++;

            if (usedNodes.Contains(sortedEdges[i][1])) numberOfExists++;

            if(numberOfExists == 1)

            {

                numberOfEdges++;

                sum += sortedEdges[i][2];

                usedNodes.Add(sortedEdges[i][0]);

                usedNodes.Add(sortedEdges[i][1]);

                sortedEdges[i] = null;

                i = -1;

            }

        }

        return sum;

    }

​

    static void Main(string[] args)

    {

​

        string[] nm = Console.ReadLine().Split(' ');

​

        int n = Convert.ToInt32(nm[0]);

​

        int m = Convert.ToInt32(nm[1]);

​

        int[][] edges = new int[m][];

​

        for (int i = 0; i < m; i++)

        {

            edges[i] = Array.ConvertAll(Console.ReadLine().Split(' '), edgesTemp => Convert.ToInt32(edgesTemp));

        }

​

        int start = Convert.ToInt32(Console.ReadLine());

​

        int result = prims(n, edges, start);

​

        Console.WriteLine(result);

        Console.Read();

​

    }

}

​