#include <cstdio>
#include <vector>

using namespace std;

#define INF 666000666
#define NMAX 30030
#define pb push_back
#define LINESIZE 30

vector<int> C[NMAX];
vector<unsigned short> A[NMAX];
unsigned short N, X, Y, Q[NMAX], G[NMAX], F[NMAX];
int M, hi, Dist[NMAX];
FILE *f;

#define read3ints(l, x, y, z) \
{ \
        int c; \
        for (c = 0; l[c] < '0' || l[c] > '9'; c++); \
        *x = 0; \
        for (;l[c] >= '0' && l[c] <= '9'; c++) \
            *x = (*x * 10) + (l[c] - '0'); \
        for (;l[c] < '0' || l[c] > '9';c++); \
        *y = 0; \
        for (;l[c] >= '0' && l[c] <= '9';c++)\
            *y = (*y * 10) + (l[c] - '0');\
        for (;l[c] < '0' || l[c] > '9';c++); \
        *z = 0; \
        for (;l[c] >= '0' && l[c] <= '9';c++)\
            *z = (*z * 10) + (l[c] - '0');\
}

#define read4ints(l, x, y, z, t)\
{ \
        int c;\
        for (c = 0; l[c] < '0' || l[c] > '9'; c++); \
        *x = 0;\
        for (;l[c] >= '0' && l[c] <= '9'; c++) \
            *x = (*x * 10) + (l[c] - '0'); \
        for (;l[c] < '0' || l[c] > '9';c++); \
        *y = 0;\
        for (;l[c] >= '0' && l[c] <= '9';c++)\
            *y = (*y * 10) + (l[c] - '0');\
        for (;l[c] < '0' || l[c] > '9';c++); \
        *z = 0;\
        for (;l[c] >= '0' && l[c] <= '9';c++)\
            *z = (*z * 10) + (l[c] - '0');\
        for (;l[c] < '0' || l[c] > '9';c++); \
        *t = 0;\
        for (;l[c] >= '0' && l[c] <= '9';c++)\
            *t = (*t * 10) + (l[c] - '0');\
}

void read()
{
        unsigned short i, j, k;
        int d;
        char line[LINESIZE];
        
        f=fopen("sate.in", "r");
//        setbuffer(f,buf,siceof(buf));
//        fscanf(f,"%d%d%d%d", &N, &M, &X, &Y);

        fgets(line, LINESIZE - 1, f);
        read4ints(line, &N, &M, &X, &Y);

        for (k = 0; k < M; k++)
        {
//                fscanf(f,"%d%d%d", &i, &j, &d);

                fgets(line, LINESIZE - 1, f);
                read3ints(line, &i, &j, &d);

                A[i].pb(j); A[j].pb(i); C[i].pb(d); C[j].pb(d);
                G[i]++; G[j]++;
                if (i==X) { Q[hi] = j; hi++; }
                if (j==X) { Q[hi] = i; hi++; }
        }
        fclose(f);
}

void solve()
{
        unsigned short i, j, f, n;
        int lo, d;

        for (i = 0; i < NMAX; i++) Dist[i] = INF;
        Dist[X] = 0;
        for (n = G[X], i = 0; i < n; i++)
            Dist[ A[X][i] ] = C[X][i];

        freopen("sate.out", "w", stdout);
        if (Dist[Y]<INF) { printf("%d\n", Dist[Y]); exit(0); }

        F[X] = 1;
        for (lo = 0; lo < hi; lo++)
        {
                i = Q[lo];
                for (n = G[i], j = 0; j < n; j++)
                {
                        f = A[i][j]; d = C[i][j];
                        if (!F[f])
                        {
                                //case 1
                                   if ( (X < i && i < f) || (X > i && i > f) ) Dist[f] = Dist[i]+d;
                                   else
                                //case 2
                                   if ( (X < f && f < i) || (X > f && f > i) ) Dist[f] = Dist[i]-d;
                                   else
                                //case 3
                                   if ( (f < X && X < i) || (i < X && X < f) ) Dist[f] = d-Dist[i];

                                Q[hi] = f; hi++;

                                F[f] = 1;
                                if (f==Y)
                                   { printf("%d\n", Dist[f]); exit(0); }
                        }
                }
        }
}

int main()
{
        read();
        solve();
        return 0;
}