#include <cstdio>
#include <algorithm>
#include <queue>

using namespace std;

#define FIN "sate.in"
#define FOUT "sate.out"

#define N 30010

int n, m, x, y, d;

vector < pair <int, int> > v[N];
vector <int> p[N];

void read()
{
    int i, a, b, c;

    freopen(FIN, "r", stdin);

    scanf("%d%d", &n, &m);
    scanf("%d%d", &a, &b);

    x = min(a, b);
    y = max(a, b);

    for (i = 1; i <= m; ++i)
    {
        scanf("%d%d%d", &a, &b, &c);

        v[a].push_back(make_pair(b, c));
        p[b].push_back(v[a].size() - 1);

        v[b].push_back(make_pair(a, c));
        p[a].push_back(v[b].size() - 1);
    }
}

int mod(int a)
{
    return a > 0 ? a : -a;
}

void DFS(int a, int d1)
{
    int i, d2, k;

    if (a == y)
        d = d1;

    for (i = 0; i < v[a].size(); ++i)
        if (v[a][i].first)
        {
            if ((x <= a && a < v[a][i].first) || (x >= a && a > v[a][i].first))
                d2 = d1 + v[a][i].second;
            else
                d2 = mod(d1 - v[a][i].second);

            k = v[a][i].first;
            v[a][i].first = 0;
            v[k][p[a][i]].first = 0;

            DFS(k, d2);
        }

    return;
}

int main()
{
    freopen(FOUT, "w", stdout);

    read();

    DFS(x, 0);

    printf("%d\n", d);
}