#include<bits/stdc++.h>
using namespace std;
const int N=1919810;
typedef long long ll;
ll n,m,x,y,k;
// int op[N],num[N];
ll a[N];
// ll x;
ll ans;
ll leave;

void cal(ll l,ll r){
    if(l>r) return;

    ll res=y+2;
    ll len=r-l+1;
    ll step=x;
    if(y-leave<x){
        step=y-leave;
    } 

    ll num=len/res;
    ans+=num*2;
    len-=num*res;
    // cout<<l<<" "<<r<<" "<<num<<endl;
    if(len>step){
        ans++;
        leave=max(0ll,len-(step+1));
    }else{
        leave=len;
    }
}

int main(){
    cin>>n>>m>>x>>y;
    for(int i=1;i<=m;i++) cin>>a[i];
    a[m+1]=n;
    for(int i=1;i<=m+1;i++){
        cal(a[i-1]+1,a[i]-1);
        // cout<<ans<<endl;        
    }
    cout<<ans<<endl;
}