#include <bits/stdc++.h> 

using namespace std;

typedef long long ll;

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

const ll inf = (ll)1e18;


ll b, p, d, n, a[N], dp[N], t[N];
ll get(ll l, ll r) {
    return r / p - (l - 1) / p;
}
ll nx(ll f) {
    return (f + p - 1) / p * p;
}
void test() {
    cin >> b >> p >> d >> n;
    for(int i = 1; i <= n; i++) {
        cin >> a[i];
    }
    a[++n] = b;
    for(int i = 1; i <= n; i++) {
        for(int j = i - 1; j >= 0; j--) {
            ll v = dp[j] + (a[i] - a[j]) + get(nx(t[j]) + 1, nx(t[j]) + a[i] - a[j] - 1) * d + nx(t[j]) - t[j];
            if(v < dp[i] || j == i - 1) {
                dp[i] = v;
                t[i] = nx(t[j]) + (a[i] - a[j]);
            }
        }
    }
    cout << dp[n] << '\n';
}

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

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

    while(t--) 
        test();

    return 0;
}