// 
#include<bits/stdc++.h>
#define ll long long
using namespace std;
const int N=1e5+10,S=1<<20;
const ll Inf=1e18;
int L,m,n,k;
ll f[S][22],g[N][22];
int cl[22];
int a[N];
ll calc(int p){
	int t=lower_bound(a+1,a+n+1,p)-a;
	return 1ll*(a[t]-p)*k;
}
map<int,int> mp;
void to(ll &x,ll y){if(x>y)x=y;}
signed main(){
	scanf("%d%d%d%d",&L,&m,&n,&k);
	for(int i=1;i<=n;i++)scanf("%d",&a[i]);
	sort(a+1,a+n+1),a[n+1]=L+a[1];
	int d=L/m;
	--m;int t=1<<m;
	for(int j=1;j<=m;j++)cl[j]=min(k==1?L:(j*d+(k-2))/(k-1),((m+1-j)*d+k)/(k+1))*k;
	for(int i=1;i<=n;i++){
		mp[a[i]]=i;
		for(int j=1;j<=m;j++){
			g[i][j]=cl[j]+calc((a[i]+j*d+cl[j]/k)%L);
		}
	}
	for(int s=1;s<t;s++)for(int j=0;j<m;j++)f[s][j]=Inf;
	for(int j=1;j<=m;j++)f[1<<j-1][j-1]=cl[j]+calc((j*d+cl[j]/k)%L);//,printf("%d %lld %lld\n",j,cl[j],(j*d+cl[j]/k)%L);
	for(int s=1;s<t;s++)for(int j=0;j<m;j++)if(f[s][j]!=Inf){
		int p=mp[((j+1)*d+f[s][j]/k)%L];
		for(int i=0;i<m;i++)if(s>>i&1^1){
			to(f[s^(1<<i)][i],f[s][j]+g[p][(i-j+m+1)%(m+1)]);
		}
	}
	ll ans=Inf;
	for(int j=0;j<m;j++)to(ans,f[t-1][j]);
	printf("%lld\n",ans);
}