#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> dp(N+1);
for (int i = N;i >= 0; i--) {
long cost = (places[i+1]-places[i]-1)/P * D + places[i+1]-places[i];
long time = places[i+1] - places[i];
long minCost = LONG_MAX;
for (int j = i+1; j < N+1 and cost < minCost; j++) {
minCost = min(minCost,dp[j] + cost + (P-time%P)%P);
cost += (places[j+1]-places[j]-1 + time%P)/P * D + places[j+1] - places[j];
time += places[j+1]-places[j];
}
dp[i] = min(minCost,cost);
}
cout << dp.front();
}
