#include <vector>

#include <iostream>

#include <queue>

#include <unordered_map>

#include <unordered_set>

using namespace std;

struct Edge

{

    Edge() :s(), t(), d() {}

    Edge(unsigned rs, unsigned rt, unsigned rd) :

        s(rs), t(rt), d(rd) {}

    unsigned s;

    unsigned t;

    unsigned d;

    bool operator()(const Edge &e1, const Edge &e2)

    {

        return e1.d > e2.d;

    }

};

int main()

{

    long n, m; cin >> n >> m;

    //    from -> to -> (length, id)

    unordered_map<unsigned, unordered_map<unsigned, unsigned>> g;

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

    {

        unsigned a, b, d; cin >> a >> b >> d;

        g[a][b] = g[b][a] = d;

    }

    unsigned s; cin >> s;

    unordered_set<unsigned> pickedSet; // linked node inx

    priority_queue<Edge, vector<Edge>, Edge> q;

    for (auto &kv : g[s])

    {

        q.push(Edge(s, kv.first, kv.second));

    }

    pickedSet.insert(s);

    unsigned long long ret = ;

    while (!q.empty())

    {

        Edge picked = q.top();

        q.pop();

        if (pickedSet.count(picked.t)) continue;

        pickedSet.insert(picked.t);

        // add new choices

        for (auto &kv : g[picked.t])

        {

            q.push(Edge(picked.t, kv.first, kv.second));

        }

        ret += picked.d;

    }

    cout << ret << endl;

    return ;

}