#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (n); i++)
#define per(i, n) for (int i = (n)-1; i >= 0; i--)
#define rep2(i, l, r) for (int i = (l); i < (r); i++)
#define per2(i, l, r) for (int i = (r)-1; i >= (l); i--)
#define each(e, v) for (auto &e : v)
#define MM << " " <<
#define pb push_back
#define eb emplace_back
#define all(x) begin(x), end(x)
#define rall(x) rbegin(x), rend(x)
#define sz(x) (int)x.size()
using ll = long long;
using pii = pair<int, int>;
using pil = pair<int, ll>;
using pli = pair<ll, int>;
using pll = pair<ll, ll>;

template <typename T>
using minheap = priority_queue<T, vector<T>, greater<T>>;

template <typename T>
using maxheap = priority_queue<T>;

template <typename T>
bool chmax(T &x, const T &y) {
    return (x < y) ? (x = y, true) : false;
}

template <typename T>
bool chmin(T &x, const T &y) {
    return (x > y) ? (x = y, true) : false;
}

template <typename T>
int flg(T x, int i) {
    return (x >> i) & 1;
}

template <typename T>
void print(const vector<T> &v, T x = 0) {
    int n = v.size();
    for (int i = 0; i < n; i++) cout << v[i] + x << (i == n - 1 ? '\n' : ' ');
    if (v.empty()) cout << '\n';
}

template <typename T>
void printn(const vector<T> &v, T x = 0) {
    int n = v.size();
    for (int i = 0; i < n; i++) cout << v[i] + x << '\n';
}

template <typename T>
int lb(const vector<T> &v, T x) {
    return lower_bound(begin(v), end(v), x) - begin(v);
}

template <typename T>
int ub(const vector<T> &v, T x) {
    return upper_bound(begin(v), end(v), x) - begin(v);
}

template <typename T>
void rearrange(vector<T> &v) {
    sort(begin(v), end(v));
    v.erase(unique(begin(v), end(v)), end(v));
}

template <typename T>
vector<int> id_sort(const vector<T> &v, bool greater = false) {
    int n = v.size();
    vector<int> ret(n);
    iota(begin(ret), end(ret), 0);
    sort(begin(ret), end(ret), [&](int i, int j) { return greater ? v[i] > v[j] : v[i] < v[j]; });
    return ret;
}

template <typename S, typename T>
pair<S, T> operator+(const pair<S, T> &p, const pair<S, T> &q) {
    return make_pair(p.first + q.first, p.second + q.second);
}

template <typename S, typename T>
pair<S, T> operator-(const pair<S, T> &p, const pair<S, T> &q) {
    return make_pair(p.first - q.first, p.second - q.second);
}

template <typename S, typename T>
istream &operator>>(istream &is, pair<S, T> &p) {
    S a;
    T b;
    is >> a >> b;
    p = make_pair(a, b);
    return is;
}

template <typename S, typename T>
ostream &operator<<(ostream &os, const pair<S, T> &p) {
    return os << p.first << ' ' << p.second;
}

struct io_setup {
    io_setup() {
        ios_base::sync_with_stdio(false);
        cin.tie(NULL);
        cout << fixed << setprecision(15);
    }
} io_setup;

const int inf = (1 << 30) - 1;
const ll INF = (1LL << 60) - 1;
// const int MOD = 1000000007;
const int MOD = 998244353;

template <typename Operator_Monoid>
struct Dual_Segment_Tree {
    using H = function<Operator_Monoid(Operator_Monoid, Operator_Monoid)>;
    int n, height;
    vector<Operator_Monoid> lazy;
    const H h;
    const Operator_Monoid e2;

    Dual_Segment_Tree(int m, const H &h, const Operator_Monoid &e2) : h(h), e2(e2) {
        n = 1, height = 0;
        while (n < m) n <<= 1, height++;
        lazy.assign(2 * n, e2);
    }

    inline void eval(int i) {
        if (i < n && lazy[i] != e2) {
            lazy[2 * i] = h(lazy[2 * i], lazy[i]);
            lazy[2 * i + 1] = h(lazy[2 * i + 1], lazy[i]);
            lazy[i] = e2;
        }
    }

    inline void thrust(int i) {
        for (int j = height; j > 0; j--) eval(i >> j);
    }

    void apply(int l, int r, const Operator_Monoid &x) {
        l = max(l, 0), r = min(r, n);
        if (l >= r) return;
        l += n, r += n;
        thrust(l), thrust(r - 1);
        while (l < r) {
            if (l & 1) lazy[l] = h(lazy[l], x), l++;
            if (r & 1) r--, lazy[r] = h(lazy[r], x);
            l >>= 1, r >>= 1;
        }
    }

    Operator_Monoid get(int i) {
        thrust(i + n);
        return lazy[i + n];
    }

    Operator_Monoid operator[](int i) { return get(i); }
};

ll solve(vector<ll> a, vector<ll> b) {
    if (sz(a) > sz(b)) swap(a, b);
    int n = sz(a), m = sz(b);
    vector<pii> c;
    rep(i, n) c.eb(a[i], 0);
    rep(i, m) c.eb(b[i], 1);
    sort(all(c));
    auto g = [](ll x, ll y) { return x + y; };
    Dual_Segment_Tree<ll> seg(m + 1, g, 0);
    vector<ll> v(m + 1, INF);
    v[0] = 0;
    int s = 0;
    rep(i, n + m) {
        auto [w, col] = c[i];
        if (col == 0) {
            seg.apply(0, s, w);
            seg.apply(s, m + 1, -w);
            s--;
        } else {
            ll tmp = (s >= 0 ? seg[s] + v[s] : 0);
            seg.apply(0, s + 1, -w);
            seg.apply(s + 1, m + 1, w);
            if (s >= 0) {
                ll now = seg[s + 1] + v[s + 1];
                if (tmp < now) seg.apply(s + 1, s + 2, tmp - now);
            }
            s++;
        }
    }
    return seg[s] + v[s];
}

int main() {
    int N, M, K;
    cin >> N >> M >> K;

    vector<ll> B(N), R(M);
    rep(i, N) cin >> B[i];
    rep(i, M) cin >> R[i];

    if (N > M) {
        swap(B, R);
        swap(N, M);
    }

    map<int, vector<ll>> mp1, mp2;
    rep(i, N) mp1[B[i] % K].eb(B[i] / K);
    rep(i, M) mp2[R[i] % K].eb(R[i] / K);

    ll ans = 0;

    each(e, mp1) {
        auto v = mp2[e.first];
        if (sz(e.second) > sz(v)) {
            cout << "-1\n";
            return 0;
        }
        ans += solve(e.second, v);
    }

    cout << ans << '\n';
}