#include<bits/stdc++.h>
using namespace std;
namespace gza{
	#define int long long
	#define R read()
	#define pb push_back
	#define MT int TTT=R;while(TTT--)
	#define pc putchar
	#define fo(i,a,b) for(int i=a;i<=b;i++)
	#define rep(i,a,b) for(int i=a;i>=b;i--)
	#define m1(a,b) memset(a,b,sizeof a)
	namespace IO
	{
		inline int read()
		{
		    int x=0;
		    char ch=getchar();
		    bool f=0;
		    while(!isdigit(ch)){if(ch=='-') f=1;ch=getchar();}
		    while(isdigit(ch)) x=(x<<1)+(x<<3)+(ch^48),ch=getchar();
		    if(f) x=-x;
		    return x;    
		}
		template<typename T> inline void write(T x)
		{
		    if(x<0) pc('-'),x=-x;
		    if(x>9) write(x/10);
		    pc(x%10+'0');
		}
	};
	namespace math
	{
		inline int gcd(int a,int b)
		{
			int az=__builtin_ctz(a),bz=__builtin_ctz(b),z=(az>bz)?bz:az,t;
		    b>>=bz;
		    while(a) a>>=az,t=a-b,b=a,az=__builtin_ctz(t<0?-t:t),a=t<0?-t:t;
		    return b<<z;
		}
		inline int qmi(int a,int b,int p)
		{
			int res=1;
			while(b)
			{
				if(b&1) res=res*a%p;
				a=a*a%p;
				b>>=1;
			}
			return res;
		}
		const int MAXN=2e6+10;
		int my_fac[MAXN],my_inv[MAXN];
		void init_binom(int mod)
		{
			my_fac[0]=1;fo(i,1,min(MAXN,mod)-1) my_fac[i]=my_fac[i-1]*i%mod;
			my_inv[min(MAXN,mod)-1]=qmi(my_fac[min(MAXN,mod)-1],mod-2,mod);rep(i,min(MAXN,mod)-2,0) my_inv[i]=my_inv[i+1]*(i+1)%mod;
		}
		int binom(int a,int b,int mod)
		{
			return my_fac[a]*my_inv[b]%mod*my_inv[a-b]%mod;
		}
	};
	using namespace IO;
	using namespace math;
	
	const int N=1e5+10;
	int b,p,d,n,ans=2e18;
	int a[N],f[N];
	void solve()
	{
		b=R,p=R,d=R,n=R;
		fo(i,1,n) a[i]=R;
		m1(f,0x5f),f[0]=0;
		// cout<<f[1]<<endl;
		fo(i,1,n) fo(j,0,i-1) f[i]=min(f[i],f[j]+a[i]-a[j]+(p-(a[i]-a[j])%p)+(a[i]-a[j]-1)/p*d);
		fo(i,0,n) ans=min(ans,f[i]+(b-a[i])+(b-a[i]-1)/p*d);
		write(ans);
	}
	void main(){
		solve();
	}
}
signed main(){
	
	gza::main();
}