#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 - max(0ll, (l - 1)) / p;
}
void test() {
    cin >> b >> p >> d >> n;
    for(int i = 1; i <= n; i++) {
        cin >> a[i];
    }

    n++;
    a[n] = b;

    for(int i = 1; i <= n; i++) {
        dp[i] = inf;
        for(int j = i - 1; j >= 0; --j) {
            ll x = get(t[j] + 1, t[j] + (a[i] - a[j]) - 1) * d;
            ll v = dp[j] + x + (a[i] - a[j]);
            if(v < dp[i]) {
                dp[i] = v;
                t[i] = t[j] + (a[i] - a[j]);        
            }
            if(x) {
                ll nx = (t[j] + p - 1) / p * p;
                v = (nx - t[j]) + get(nx + 1, nx + (a[i] - a[j]) - 1) * d + (a[i] - a[j]) + dp[j];
                if(v < dp[i]) {
                    dp[i] = v;
                    t[i] = nx + (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;
}