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

using namespace std;

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

#define N 30010
#define MAX 60

int m, d;
short int x, y, n;

vector < short int > v[N], p[N];
vector <int> ds[N];

void read()
{
    int i, j, a[3], nr;
	char s[MAX];

    freopen(FIN, "r", stdin);

    scanf("%hd%d", &n, &m);
    scanf("%hd%hd\n", &a[0], &a[1]);

    x = min(a[0], a[1]);
    y = max(a[0], a[1]);

    for (i = 1, nr = 0; i <= m; ++ i)
    {
        gets(s);

		a[0] = a[1] = a[2] = 0;

        for (j = 0, nr = 0 ; s[j] && s[j] != 13; ++ j)
		{
			if (s[j] == ' ')
				++ nr;
			else
				a[nr] = a[nr] * 10 + (s[j] - '0');
		}

		v[a[0]].push_back(a[1]);
		ds[a[0]].push_back(a[2]);
        p[a[1]].push_back(v[a[0]].size() - 1);

        v[a[1]].push_back(a[0]);
        ds[a[1]].push_back(a[2]);
        p[a[0]].push_back(v[a[1]].size() - 1);

		scanf("\n");
    }
}

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

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

    if (a == y)
        d = d1;

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

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

            DFS(k, d2);
        }

    return;
}

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

    read();

    DFS(x, 0);

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