#include <bits/stdc++.h>
using namespace std;

#define int long long

#define INF (int)1e18

struct DSU {
	vector<int> v;

	DSU(int n) : v(n + 1, -1) {
	}

	int find(int a) {
		return v[a] < 0 ? a : v[a] = find(v[a]);
	}

	void unite(int a, int b) {
		a = find(a);
		b = find(b);
		if (a == b) {
			return;
		}
		if (v[a] > v[b]) {
			swap(a, b);
		}
		v[a] += v[b];
		v[b] = a;
	}
};

template<typename T>
using min_priority_queue=priority_queue<T,vector<T>,greater<T>>;

signed main(){
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	int N,M,A,B;
	cin>>N>>M>>A>>B;
	vector<vector<pair<int,int>>>g(N+1);
	for(int i=0;i<M;i++){
		int a,b,w;
		cin>>a>>b>>w;
		g[a].emplace_back(b,w);
		g[b].emplace_back(a,w);
	}
	vector<int>c(N+1,INF);
	min_priority_queue<pair<int,int>>pq;
	c[B]=0;
	pq.emplace(0,B);
	while(!pq.empty()){
		auto[d,i]=pq.top();
		pq.pop();
		if(d>c[i]){
			continue;
		}
		for(auto[j,w]:g[i]){
			if(c[i]+w<c[j]){
				c[j]=c[i]+w;
				pq.emplace(c[j],j);
			}
		}
	}
	vector<int>v(N+1);
	DSU dsu(N+1);
	auto dfs1=[&](auto self,int i)->void{
		if(v[i]){
			return;
		}
		v[i]=1;
		for(auto[j,_]:g[i]){
			if(c[j]==c[i]){
				dsu.unite(i,j);
			}
			if(c[j]<=c[i]){
				self(self,j);
			}
		}
	};
	dfs1(dfs1,A);
	vector<set<int>>gg(N+1);
	for(int i=1;i<=N;i++){
		for(auto[j,_]:g[i]){
			if(c[j]<=c[i]&&dsu.find(j)!=dsu.find(i)){
				gg[dsu.find(i)].insert(dsu.find(j));
			}
		}
	}
	vector<int>w(N+1),u(N+1);
	auto dfs2=[&](auto self,int i)->void{
		if(w[i]){
			return;
		}
		int x=0;
		for(int j:gg[i]){
			self(self,j);
			if(w[j]>x){
				x=w[j];
				u[i]=j;
			}
		}
		w[i]=-dsu.v[dsu.find(i)]+x;
	};
	dfs2(dfs2,dsu.find(A));
	vector<int>y(N+1);
	for(int i=dsu.find(A);i;i=u[i]){
		y[i]=1;
	}
	cout<<w[dsu.find(A)]<<'\n';
	for(int i=1;i<=N;i++){
		if(y[dsu.find(i)]){
			cout<<i<<' ';
		}
	}
	cout<<'\n';
	return 0;
}