#include <bits/stdc++.h> 

using namespace std;

typedef long long ll;

const int N = (int)1e6 + 12;

const ll inf = 11e17;

ll b, p, d, n, a[N], m;
ll dp[N];
vector<ll> c;
struct segtree{
    vector<ll> t;
    void init() {
        t.assign(m * 4, inf);
    }
    void upd(int pos, ll val, int v = 1, int tl = 0, int tr = m - 1) {
        if(tl == tr) {
            t[v] = min(t[v], val);
        } else {
            int tm = (tl + tr) >> 1;
            if(pos <= tm) upd(pos, val, v + v, tl, tm);
            else upd(pos, val, v + v + 1, tm + 1, tr);
            t[v] = min(t[v + v], t[v + v + 1]);
        }
    }
    ll get(int l, int r, int v = 1, int tl = 0, int tr = m - 1) {
        if(l > r || tl > r || l > tr) return inf;
        if(tl >= l && tr <= r) return t[v];
        int tm = (tl + tr) >> 1;
        return min(get(l, r, v + v, tl, tm), get(l, r, v + v + 1, tm + 1, tr));
    }
}pr, sf;

void upd_pr(ll i) {
    int it = lower_bound(c.begin(), c.end(), a[i] % p) - c.begin();
    pr.upd(it, dp[i] - (a[i] / p) * d + a[i] % p);
}
void upd_sf(ll i) {
    int it = lower_bound(c.begin(), c.end(), a[i] % p) - c.begin();
    sf.upd(it, dp[i] + a[i] % p - (a[i] / p) * d);
}
ll get_pr(ll i) {
    int it = lower_bound(c.begin(), c.end(), a[i] % p) - c.begin();
    return pr.get(0, it - 1) + (a[i] / p) * d + p - (a[i] % p);
}
ll get_sf(ll i) {
    int it = lower_bound(c.begin(), c.end(), a[i] % p) - c.begin();
    return sf.get(it, m - 1) + (a[i] / p) * d - d - (a[i] % p);
}
void test() {
    cin >> b >> p >> d >> n;
    for(int i = 1; i <= n; i++) {
        cin >> a[i];
        c.push_back(a[i] % p);
    }
    c.push_back(0);
    sort(c.begin(), c.end());
    c.resize(unique(c.begin(), c.end()) - c.begin());
    m = (int)c.size();
    pr.init();
    sf.init();
    upd_pr(0);
    upd_sf(0);
    for(int i = 1; i <= n; i++) {
        dp[i] = min(get_pr(i), get_sf(i));
        upd_pr(i);
        upd_sf(i);
    }
    ll res = inf;
    for(int i = 0; i <= n; i++) {
        ll r = b - a[i] - 1;
        res = min(res, dp[i] + (r / p)  * d);
    }
    cout << res + b << '\n';
}

int32_t main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0);

    int t = 1;
    // cin >> t;

    while(t--) 
        test();

    return 0;
}