#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);
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] <= c)
continue;
values[p.second] = c;
if (p.second == N+1)
break;
const long dist = places[p.second+1] - places[p.second];
pq.emplace(c + (dist + p.first % P - 1) / P * D + dist,make_pair(p.first + dist,p.second+1));
pq.emplace(c+(dist-1)/P*D + P - p.first % P + dist,make_pair(p.first + P - p.first%P + dist, p.second+1));
}
cout << values.back();
}
