#include <bits/stdc++.h>
using namespace std;
const int N=5e4;
int n,cn,fn,m,c[N],dp[N];
bool vis[N];
unordered_map<int , bool>mp;
int dfs(int x)
{
	if(vis[x]){ printf("-1\n");exit(0); }
	if(dp[x]) return dp[x];
	vis[x]=1;
	if(mp[x] && x!=n) dp[x]=max(dp[x],dfs(x+m));
	for(int i=1;i<=cn;i++) if(x>=c[i]) dp[x]=max(dp[x],c[i]+dfs(x-c[i]));
	vis[x]=0;//这里设置vis为0，才能让vis=1成为判断环的条件
	return dp[x];
}
int main()
{
	scanf("%d%d%d%d",&n,&cn,&fn,&m);
	for(int i=1;i<=cn;i++)scanf("%d",&c[i]);
	for(int i=1,x;i<=fn;i++)scanf("%d",&x), mp[x]=1;
	memset(dp,0,sizeof dp);
	printf("%d\n", dfs(n) );
	return 0;
}

#include <bits/stdc++.h>
using namespace std;
const int N=5e4;
int n,cn,fn,m,c[N],dp[N];
bool vis[N];
unordered_map<int , bool>mp;
int dfs(int x)
{
	if(vis[x]){ printf("-1\n");exit(0); }
	if(dp[x]) return dp[x];
	vis[x]=1;
	if(mp[x] && x!=n) dp[x]=max(dp[x],dfs(x+m));
	for(int i=1;i<=cn;i++) if(x>=c[i]) dp[x]=max(dp[x],c[i]+dfs(x-c[i]));
	vis[x]=0;//这里设置vis为0，才能让vis=1成为判断环的条件
	return dp[x];
}
int main()
{
	scanf("%d%d%d%d",&n,&cn,&fn,&m);
	for(int i=1;i<=cn;i++)scanf("%d",&c[i]);
	for(int i=1,x;i<=fn;i++)scanf("%d",&x), mp[x]=1;
	memset(dp,0,sizeof dp);
	printf("%d\n", dfs(n) );
	return 0;
}