#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const ll oo = (1e+18);
const int maxn = 1000009;
ll dpx[maxn];
ll T[maxn];
ll S = 0;
const ll base = (1<<20);
ll Rt[base*2];
void U(int X)
{
X /= 2;
while(X)
{
Rt[X] = min(Rt[2*X] , Rt[2*X+1]);
X /= 2;
}
}
ll Q(ll l , ll r)
{
ll res = oo;
l += base , r+= base;
l--;
r++;
while(l/2 != r/2)
{
if((l&1) == 0)res = min(res,Rt[l+1]);
if((r&1) == 1)res = min(res,Rt[r-1]);
l /= 2;
r /= 2;
}
return res;
}
int main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
ll n , b , d , p;
cin >> b >> p >> d >> n;
n++;
T[0] = 0;
T[n] = b;
for(int i = 1; i < n ; i++)
{
cin >> T[i];
}
for(int j =0 ; j < 2*base ; j++)Rt[j] = oo;
dpx[n] = oo;
for(int i = n-1 ; i >= 0 ; i--)
{
ll A = T[i+1]-T[i];
S += A;
dpx[i] = S+S/p*d;
if(S%p == 0)dpx[i] -= d;
ll Fie = 0;
ll Sg = S/p*d + S - S%p;
if(S%p-1 >= 0)dpx[i] = min(dpx[i] , Sg + Q(0 + 1 , S%p-1 + 1) + p);
dpx[i] = min(dpx[i] , Sg + Q(S%p + 1 , p + 1) - d);
Rt[S%p + base + 1] = min(Rt[S%p + base + 1] , dpx[i] - (S/p*d) - S + S%p);
U(S%p + base + 1);
}
cout << dpx[0] << '\n';
return 0;
}
