#include<algorithm>

#include<cstring>

#include<iostream>

#include<cstdio>

using namespace std;

const int N=+;

const int inf=1e9+;

const int Inf=;

int v,e,n,k;

int pos[N],d[N][N],mp[N][N],match[N],vis[N];

inline int read()

{

    char ch=getchar();

    int s=,f=;

    while (ch<''||ch>'') {if (ch=='-') f=-;ch=getchar();}

    while (ch>=''&&ch<='') {s=(s<<)+(s<<)+ch-'';ch=getchar();}

    return s*f;

}

void floyd()

{

    for (int k=;k<=v;k++)

        for (int i=;i<=v;i++)

            for (int j=;j<=v;j++) d[i][j]=min(d[i][j],d[i][k]+d[k][j]);

}

bool dfs(int x)

{

    for (int i=;i<=v;i++)

    {

        if (vis[i]||!mp[x][i]) continue;

        vis[i]=;

        if (match[i]==-||dfs(match[i]))

        {

            match[i]=x;

            return true;

        }

    }

    return false;

}

int check(int l)

{

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

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

        for (int j=;j<=v;j++)

         mp[i][j]=(d[pos[i]][j]<=l);

    int ans=;

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

    {

        memset(vis,,sizeof(vis));

        if (dfs(i)) ans++;

    }

    return ans;

}

int main()

{

    v=read();e=read();n=read();k=read();

    for (int i=;i<=v;i++)

        for (int j=;j<=v;j++) if (i!=j) d[i][j]=inf;

    for (int i=;i<=n;i++) pos[i]=read();

    for (int i=,u,v,w;i<=e;i++)

    {

        u=read();v=read();w=read();

        d[u][v]=d[v][u]=min(d[u][v],w);

    }

    floyd();

    int l=,r=Inf,ans=Inf;

    while (l<r)

    {

        int mid=l+r>>;

        if (check(mid)>=k) r=mid,ans=min(ans,r);

        else l=mid+;

    }

    if (ans==Inf) puts("-1");

    else printf("%d\n",ans);

    return ;

}