import java.util.*;
class Pair{
    int a;
    int b;
    public Pair(int a, int b){
        this.a = a;
        this.b = b;
    }
}
public class Main{
    public static final int N = 6210 * 2 , max = 0x3f3f3f3f;
    public static int[] e = new int[N];
    public static int[] ne = new int[N];
    public static int[] h = new int[N];
    public static int[] w = new int[N];
    public static int[] dist = new int[N];
    public static boolean[] feasible = new boolean[N];
    public static int n , m , s , r , idx = 0;

    public static void add(int a , int b , int c){
        e[idx] = b;
        ne[idx] = h[a];
        w[idx] = c;
        h[a] = idx++;
    }

    public static int dijkstra(){
        PriorityQueue<Pair> q = new PriorityQueue<>((p1 , p2) -> {return p1.a - p2.a;});
        Arrays.fill(dist , max);
        dist[s] = 0;
        q.offer(new Pair(0 , s));
        while(q.size() != 0)
        {
            Pair t = q.poll();
            int distance = t.a;
            int num = t.b;
            if(feasible[num]) continue;
            feasible[num] = true;
            for(int i = h[num] ; i != -1 ; i = ne[i])
            {
                int j = e[i];
                if(dist[j] > distance + w[i])
                {
                    dist[j] = distance + w[i];
                    q.offer(new Pair(dist[j] , j));
                }
            }
        }
        return dist[r];
    }

    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        n = sc.nextInt();
        m = sc.nextInt();
        s = sc.nextInt();
        r = sc.nextInt();
        Arrays.fill(h , -1);
        while(m -- > 0)
        {
            int a = sc.nextInt();
            int b = sc.nextInt();
            int c = sc.nextInt();
            // 是双向道路,记得加入a->b b-> 两条边
            add(a , b , c);
            add(b , a , c);
        }
        int t = dijkstra();
        System.out.println(t);
    }
}