import java.io.*;
import java.util.*;

public class Rts {

	public static void main(String args[]) throws Exception {

		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		PrintWriter pw = new PrintWriter(new BufferedWriter(new OutputStreamWriter(System.out)));
		StringTokenizer st = new StringTokenizer(br.readLine());
		
		int n = Integer.parseInt(st.nextToken()), m = Integer.parseInt(st.nextToken()), a = Integer.parseInt(st.nextToken()), b = Integer.parseInt(st.nextToken());

		a--;
		b--;
		
		int[][] w = new int[n][n];
		int[] lens = new int[n];
		HashSet<Edge>[] prevs = new HashSet[n];
		
		for(int i = 0; i < n; i++)
			prevs[i] = new HashSet<Edge>();
		
		for(int i = 0; i < n; i++)
			Arrays.fill(w[i], -1);
		
		int lsum = 0;
		
		for(int i = 0; i < m; i++) {
			st = new StringTokenizer(br.readLine());
			
			int u = Integer.parseInt(st.nextToken())-1;
			int v = Integer.parseInt(st.nextToken())-1;
			int l = Integer.parseInt(st.nextToken());
			
			lsum += l;
			
			w[u][v] = l;
			w[v][u] = l;
		}		
		
		PriorityQueue<int[]> pq = new PriorityQueue<int[]>(new Comparator<int[]>() {
			@Override
			public int compare(int[] a, int[] b) {
				// TODO Auto-generated method stub
				return Integer.compare(a[1], b[1]);
			}			
		});
		
		Arrays.fill(lens, 1000000000);
		
		lens[a] = 0;
		
		pq.add(new int[] {a, 0});
		
		while(!pq.isEmpty()) {
			int[] cur = pq.poll();
			
			if(lens[cur[0]] < cur[1])
				continue;
			
			for(int i = 0; i < n; i++) {
				if(w[cur[0]][i] == -1)
					continue;
				
				if(cur[1] + w[cur[0]][i] < lens[i]) {
					lens[i] = cur[1] + w[cur[0]][i];
					prevs[i].clear();
					
					prevs[i].addAll(prevs[cur[0]]);
					prevs[i].add(new Edge(cur[0], i));
					
					pq.add(new int[] {i, lens[i]});
				}else if(cur[1] + w[cur[0]][i] == lens[i]) {
					prevs[i].addAll(prevs[cur[0]]);
					prevs[i].add(new Edge(cur[0], i));
				}
			}
		}
				
		for(Edge e : prevs[b])
			lsum -= w[e.from][e.to];
		
		pw.println(lsum);
		pw.close();
	}
	
	static class Edge{
		int to, from;
		
		public Edge(int f, int t) {
			to = t;
			from = f;
		}

		@Override
		public int hashCode() {
			// TODO Auto-generated method stub
			return to * 100 + from;
		}				
	}
}