#include <bits/stdc++.h>
#include <cassert>

using namespace std;
using ll = long long;

#define all(x) (x).begin(), (x).end()
#define sz(x) (int)(x).size()
#define pb push_back
#define ff first
#define sc second
#define int ll

mt19937 rnd(time(NULL));
template<typename T>
void shuf(vector<T>& a) {
    for (int i = 1; i < sz(a); i++) swap(a[i], a[rnd() % (i + 1)]);
}

void solve() {
    int b, p, d, n; cin >> b >> p >> d >> n;
    vector<int> a(n + 2);
    for (int i = 1; i <= n; i++) cin >> a[i];
    a[n + 1] = b;
    
    vector<int> dp(n + 2, 0);
    for (int i = n; i >= 0; i--) {
        dp[i] = 1e18;
        for (int nxt = i + 1; nxt <= n + 1; nxt++) {
            int path = (a[nxt] - a[i] + p - 1) / p * p;
            if (nxt == n + 1) path = a[nxt] - a[i];
            int pts = (a[nxt] - a[i] - 1) / p;
            dp[i] = min(dp[i], dp[nxt] + path + pts * d);
        }
    }
    cout << dp[0] << '\n';
}

signed main() {
    int tt = 1;
    #ifdef LOCAL 
        freopen("in.txt", "r", stdin);
        freopen("out.txt", "w", stdout);
        cin >> tt;
    #else
        ios::sync_with_stdio(false); 
        cin.tie(0); cout.tie(0);
    #endif

    while (tt--) {
        solve();
    }

    return 0;
}