#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define int ll
using pii = pair<int, int>;
constexpr int nax = 1e6 + 5;
signed main() {
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
int n, t, k;
cin >> n >> t >> k;
vector<int> cost(k);
for(int& i : cost) {
cin >> i;
}
vector<int> idx(nax, 0);
priority_queue<pii, vector<pii>, greater<pii>> q;
for(int i = 0; i < nax; i++) {
q.push({cost[0]+t*i, i});
}
ll ans = 0;
int p = 0;
while(p < n) {
assert(!q.empty());
auto v = q.top();
q.pop();
int take = min(n-p, (v.second + 1) * 4LL);
ans += v.first * take;
p += take;
idx[v.second]++;
if (idx[v.second] < k) {
q.push({cost[idx[v.second]] + v.second * t, v.second});
}
// cout << p <<
}
cout << ans << "\n";
// cout << p << " " << ans << "\n";
return 0;
}
