#include <bits/stdc++.h>

#define FOR(i,a,b) for(int i= (a); i<((int)b); ++i)
#define RFOR(i,a) for(int i=(a); i >= 0; --i)
#define FOE(i,a) for(auto i : a)
#define ALL(c) (c).begin(), (c).end()
#define RALL(c) (c).rbegin(), (c).rend()
#define DUMP(x)  cerr << #x << " = " << (x) << endl;
#define SUM(x) std::accumulate(ALL(x), 0LL)
#define MIN(v) *std::min_element(v.begin(), v.end())
#define MAX(v) *std::max_element(v.begin(), v.end())
#define EXIST(v,x) (std::find(v.begin(), v.end(), x) != v.end())
#define BIT_ON(bit, i) (bit & (1LL << i))

typedef long long LL;
template<typename T> using V = std::vector<T>;
template<typename T> using VV = std::vector<std::vector<T>>;
template<typename T> using VVV = std::vector<std::vector<std::vector<T>>>;
template<typename T> using VVVV = std::vector<std::vector<std::vector<std::vector<T>>>>;

template<class T> inline T ceil(T a, T b) { return (a + b - 1) / b; }
template<class T> inline void print(T x) { std::cout << x << std::endl; }
template<class T> inline void print_vec(const std::vector<T> &v) { for (int i = 0; i < v.size(); ++i) {  if (i != 0) {std::cout << " ";} std::cout << v[i];} std::cout << "\n"; }
template<class T> inline bool inside(T y, T x, T H, T W) {return 0 <= y and y < H and 0 <= x and x < W; }
template<class T> inline double euclidean_distance(T y1, T x1, T y2, T x2) { return sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2)); }
template<class T> inline double manhattan_distance(T y1, T x1, T y2, T x2) { return abs(x1 - x2) + abs(y1 - y2); }
template<class T> inline std::vector<T> unique(std::vector<T> v) {
    sort(v.begin(), v.end());
    v.erase(unique(v.begin(), v.end()), v.end());
    return v;
}
// 初項s, 交差dのn個の数列の和
long long sum_of_arithmetic_progression(long long s, long long d, long long n) {
    return n * (2 * s + (n - 1) * d) / 2;
}

const int INF = 1 << 30;
const double EPS = 1e-9;
const std::string YES = "YES", Yes = "Yes", NO = "NO", No = "No";
const std::vector<int> dy4 = { 0, 1, 0, -1 }, dx4 = { 1, 0, -1, 0 };    // 4近傍（右, 下, 左, 上）
const std::vector<int> dy8 = { 0, -1, 0, 1, 1, -1, -1, 1 }, dx8 = { 1, 0, -1, 0, 1, 1, -1, -1 };

using namespace std;

class CumulativeSum {

public:
    std::vector<long long> memo1;               // 1次元用の累積和表
    std::vector<std::vector<long long>> memo2;  // 2次元用の累積和表

    CumulativeSum() {}

    void build(const std::vector<long long> &line) {
        this->memo1.assign(line.size() + 1, 0);

        for (long long i = 0; i < line.size(); ++i) {
            this->memo1[i + 1] = this->memo1[i] + line[i];
        }
    }

    // 2次元の累積和表を作成
    void build(const std::vector<std::vector<long long>> &board) {
        int height = board.size();
        int width = board[0].size();
        this->memo2.assign(height + 1, std::vector<long long>(width + 1, 0));

        for (int y = 0; y < height; ++y) {
            for (int x = 0; x < width; ++x) {
                memo2[y + 1][x + 1] = board[y][x] + memo2[y + 1][x];
            }
            for (int x = 0; x < width; ++x) {
                memo2[y + 1][x + 1] += memo2[y][x + 1];
            }
        }
    }

    long long sum(int left, int right) {
        assert(left < right);
        return this->memo1[right] - this->memo1[left];
    }

    /*
    (y1, x1)から(y2, x2)の合計を返す．(y2, x2)は含まない
    座標はmemoを作成したboard準拠
    (ex, sum(0, 0, 2, 2)なら(0, 0), (0, 1), (1, 0), (1, 1)の合計を返す)
    */
    long long sum(int y1, int x1, int y2, int x2) {
        return this->memo2[y2][x2] - this->memo2[y2][x1] - this->memo2[y1][x2] + this->memo2[y1][x1];
    }
};


LL dfs(int left, int right, int N, int L, V<int> &K, CumulativeSum &cost, VV<LL> &dp) {
    int next = max(left, right) + 1;

    if (dp[left][right] != -1) {
        return dp[left][right];
    }

    if (next == N - 1) {
        return (cost.sum(K[left], K[next] + 1) / L) + (cost.sum(K[right], K[next] + 1) / L);
    }

    LL ans = LONG_LONG_MAX;

    // leftにいれる
    ans = min(ans, dfs(next, right, N, L, K, cost, dp) + (cost.sum(K[left], K[next] + 1) / L));
    // rightにいれる
    ans = min(ans, dfs(left, next, N, L, K, cost, dp) + (cost.sum(K[right], K[next] + 1) / L));

    return dp[left][right] = ans;
}

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);

    int N, M, L;
    cin >> N >> M >> L;
    V<int> K(N);
    V<LL> S(M);
    FOR(i, 0, N) {
        cin >> K[i];
        K[i]--;
    }
    sort(ALL(K));

    FOR(i, 0, M) {
        cin >> S[i];
    }

    CumulativeSum cs;
    cs.build(S);

    VV<LL> dp(N + 1, V<LL>(N + 1, -1));
    print(dfs(0, 0, N, L, K, cs, dp));

    return 0;
}


Measured memory_bytes: 36208