#include <bits/stdc++.h>
using namespace std;
int main() {
long B, P, D, N;
cin >> B >> P >> D >> N;
vector<long> places(N + 2);
places[0] = 0, places.back() = B;
for (int i = 0; i < N; i++)
cin >> places[i + 1];
vector<long> values(N + 2,LONG_MAX-D);
priority_queue<pair<long, pair<long, int> >, vector<pair<long, pair<long, int> > >, greater<> > pq;
pq.emplace(places[1] + (places[1] - 1) / P * D, make_pair(places[1], 1));
while (!pq.empty()) {
auto [c,p] = pq.top();
pq.pop();
if (values[p.second] + D <= c)
continue;
values[p.second] = min(c,values[p.second]);
if (p.second == N + 1)
break;
const long dist = places[p.second + 1] - places[p.second];
const long cost1 = c + (dist + p.first % P - 1) / P * D + dist;
pq.emplace(cost1, make_pair(p.first + dist, p.second + 1));
if (const long cost2 = c + (dist - 1) / P * D + P - p.first % P + dist; cost2 < cost1 + P - p.first % P)
pq.emplace(cost2,make_pair(p.first + P - p.first % P + dist, p.second + 1));
}
cout << values.back();
}
