#include<bits/stdc++.h>
using namespace std;
#define int long long
//#define ll long long
const int N = 2e5 + 10;
vector<int> blk;
int n, m, x, y, ans, lst, now;
void calc(int l, int n){
	ans += 2 * (n / (y + 2));	
	n %= (y + 2);
	if(n > (l + 1)){
		ans ++;
		lst = (n - (l + 1));
	}
	else lst = n;
}
void solve(){
	cin >> n >> m >> x >> y;
	for(int i = 1 ; i <= m ; i ++){
		cin >> now;
		blk.push_back(now - lst - 1);
		lst = now;
	}
	blk.push_back(n - lst);
	lst = 0;
	for(int i = 0 ; i <= m ; i ++){
		int fir = min(x, y - lst);
		if(blk[i] <= fir){
			lst = blk[i];
			continue;
		}
		ans ++; blk[i] -= fir + 1; lst = fir;
		calc(y - fir, blk[i]);
//		cout << i << ' ' << blk[i] << ' ' << ans << '\n';
	}
	cout << ans << '\n';
}

signed main(){
	solve();
}