// 
#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define For(i,a,b) for(int i=(a);i<=(b);i++)
#define dFor(i,a,b) for(int i=(a);i>=(b);i--)
#define tomin(x,y) x=min(x,y)
#define tomax(x,y) x=max(x,y)
#define ll long long
#define db double
#define pb push_back
#define gc getchar
const int N=1e5+5;
const ll I=1e18;
int read()
{
	int x=0,y=1;
	char c=getchar();
	for(;!isdigit(c);c=getchar()) if(c=='-') y=0;
	for(;isdigit(c);c=getchar()) x=(x<<3)+(x<<1)+(c^48);
	return y?x:-x;
}
int L,R,n,K,m;
int a[N];
ll g[N][22];
ll f[1<<20|5][22];
map<int,int> mp;
int get1(int st,int ed)
{
	if(st<=ed) return ed-st;
	return L-st+ed;
}
int go(int u,int k) { return (u+k+L)%L; }
int lb(int x)
{
	if(x<=a[n]) return lower_bound(a+1,a+n+1,x)-a;
	return 1;
}
void pre()
{
	memset(g,63,sizeof(g));
	For(i,0,n)
	{
		For(j,1,R-1)
		{
			int nw=a[i],to=(nw+j*m)%L;
			int t2=(get1(to,nw)+K)/(K+1);
			int t3=go(to,t2);
			int t4=lb(t3);
//			cout<<get1(to,nw)<<" "<<t2<<" "<<t3<<" "<<t4<<endl;
			ll as1=t2+get1(t3,a[t4]);
			
			if(K>1)
			{
				int t2=(get1(nw,to)+K-2)/(K-1);
				int t3=go(to,t2);
				int t4=lb(t3);
				ll as2=t2+get1(t3,a[t4]);
				tomin(as1,as2);
//				cout<<"         "<<as1<<" "<<as2<<endl;
			}
			tomin(g[i][j],as1*K);
//			cout<<i<<" "<<j<<" "<<g[i][j]<<endl;
		}
	}
}
signed main()
{
//	freopen("P10285_17.in","r",stdin);
//	freopen("P10285.out","w",stdout);
	L=read(),R=read(),n=read(),K=read();
	m=L/R; int up=(1<<R)-1;
	For(i,1,n) a[i]=read();
	sort(a+1,a+n+1); n=unique(a+1,a+n+1)-a-1;
	For(i,1,n) mp[a[i]]=i;
	pre();
//	For(i,1,n)
//	{
//		For(j,1,R-1) printf("%lld ",g[i][j]); puts("");
//	}
	memset(f,63,sizeof(f));
	f[1][1]=0;
	for(int k=1;k<=up;k+=2) For(i,1,R) if((k>>i-1&1)&&f[k][i]<f[0][0])
	{
		ll t=f[k][i];
		int nw=mp[((i-1ll)*m+t/K)%L];
		For(j,1,R) if((k>>j-1&1^1))
		{
//			cout<<i<<" "<<j<<" "<<t<<" "<<g[nw][(j+R-i)%R]<<endl;
			tomin(f[k|1<<j-1][j],t+g[nw][(j+R-i)%R]);
		}
	}
	ll ans=I;
	For(i,1,R) tomin(ans,f[up][i]);
	printf("%lld\n",ans);
	return 0;
} 
/*
4
1 3
2 5
4 8
6 7

*/