Description：

Solution：

Code：

#include<algorithm>

#include<iostream>

#include<cstdlib>

#include<cstdio>

#include<cmath>

#include<cctype>

#include<cstring>

using namespace std;

int n,m,s,w;

#define MAXN 610

int p[MAXN];

int f[MAXN][MAXN];

struct edge

{

	int to,nxt;

}e[MAXN * MAXN];

int edgenum = 0;

int lin[MAXN] = {0};

void add(int a,int b)

{

	e[++edgenum] = (edge){b,lin[a]};lin[a] = edgenum;

	return;

}

int match[MAXN];

bool v[MAXN];

bool find(int k)

{

	for(int i = lin[k];i != 0;i = e[i].nxt)

	{

		if(!v[e[i].to])

		{

			v[e[i].to] = true;

			if(match[e[i].to] == -1 || find(match[e[i].to]))

			{

				match[e[i].to] = k;

				return true;

			}

		}

	}

	return false;

}

bool check(int k)

{

	memset(lin,0,sizeof(lin));

	edgenum = 0;

	for(int i = 1;i <= s;++i)

		for(int j = 1;j <= n;++j)

			if(f[p[i]][j] <= k)add(i,j);

	int ans = 0;

	memset(match,-1,sizeof(match));

	for(int i = 1;i <= s;++i)

	{

		memset(v,false,sizeof(v));

		if(find(i))++ans;

	}

	return (ans >= w);

}

int main()

{

	scanf("%d%d%d%d",&n,&m,&s,&w);

	for(int i = 1;i <= s;++i)scanf("%d",&p[i]);

	memset(f,0x3f,sizeof(f));

	for(int i = 1;i <= n;++i)f[i][i] = 0;

	int a,b,c;

	for(int i = 1;i <= m;++i)

	{

		scanf("%d%d%d",&a,&b,&c);

		f[a][b] = f[b][a] = min(f[a][b],c);

	}

	for(int k = 1;k <= n;++k)

		for(int i = 1;i <= n;++i)

			for(int j = 1;j <= n;++j)

				f[i][j] = min(f[i][j],f[i][k] + f[k][j]);

	int l = 0,r = 100000000,mid;

	while(l < r)

	{

		mid = ((l + r) >> 1);

		if(check(mid))r = mid;

		else l = mid + 1;

	}

	if(l != 100000000)cout << l << endl;

	else puts("-1");

	return 0;

}