#include <iostream>
#include <map>
#include <vector>

//#define NDEBUG

#include <algorithm>
#include <cassert>
#include <cstddef>
#include <cstdint>
#include <iostream>
#include <utility>
#include <vector>

namespace n91 {

  using i32 = std::int32_t;
  using i64 = std::int64_t;
  using u32 = std::uint32_t;
  using u64 = std::uint64_t;
  using isize = std::ptrdiff_t;
  using usize = std::size_t;

  struct rep {
    struct itr {
      usize i;
      constexpr itr(const usize i) noexcept : i(i) {}
      void operator++() noexcept { ++i; }
      constexpr usize operator*() const noexcept { return i; }
      constexpr bool operator!=(const itr x) const noexcept { return i != x.i; }
    };
    const itr f, l;
    constexpr rep(const usize f, const usize l) noexcept
      : f(std::min(f, l)), l(l) {}
    constexpr auto begin() const noexcept { return f; }
    constexpr auto end() const noexcept { return l; }
  };
  struct revrep {
    struct itr {
      usize i;
      constexpr itr(const usize i) noexcept : i(i) {}
      void operator++() noexcept { --i; }
      constexpr usize operator*() const noexcept { return i; }
      constexpr bool operator!=(const itr x) const noexcept { return i != x.i; }
    };
    const itr f, l;
    constexpr revrep(const usize f, const usize l) noexcept
      : f(l - 1), l(std::min(f, l) - 1) {}
    constexpr auto begin() const noexcept { return f; }
    constexpr auto end() const noexcept { return l; }
  };
  template <class T> auto md_vec(const usize n, const T& value) {
    return std::vector<T>(n, value);
  }
  template <class... Args> auto md_vec(const usize n, Args... args) {
    return std::vector<decltype(md_vec(args...))>(n, md_vec(args...));
  }
  template <class T> constexpr T difference(const T& a, const T& b) noexcept {
    return a < b ? b - a : a - b;
  }
  template <class T> void chmin(T& a, const T& b) noexcept {
    if (b < a)
      a = b;
  }
  template <class T> void chmax(T& a, const T& b) noexcept {
    if (a < b)
      a = b;
  }
  template <class F> class rec_lambda {
    F f;

  public:
    rec_lambda(F&& f) : f(std::move(f)) {}
    template <class... Args> auto operator()(Args &&... args) const {
      return f(*this, std::forward<Args>(args)...);
    }
  };
  template <class F> auto make_rec(F&& f) { return rec_lambda<F>(std::move(f)); }
  template <class T> T scan() {
    T ret;
    std::cin >> ret;
    return ret;
  }
  constexpr char eoln = '\n';
  template <class T> T ceildiv(const T& l, const T& r) {
    return l / r + (l % r != 0 ? 1 : 0);
  }

} // namespace n91

#include <deque>

namespace n91 {

  void main_() {

    const auto solve = [](std::vector<int> lxt, std::vector<int> rxt) {
      struct vtx {
        int type; // 0:a, 1:b
        i64 v;
      };
      std::vector<vtx> vs;
      for (const auto e : lxt) {
        vs.push_back({ 0, e });
      }
      for (const auto e : rxt) {
        vs.push_back({ 1, e });
      }
      std::sort(vs.begin(), vs.end(),
        [](const auto& l, const auto& r) { return l.v < r.v; });

      struct aque {
        std::deque<std::pair<i64, i64>> v;
        i64 a;

        aque() : v(), a(0) {}

        void push_front(i64 x, i64 l) { v.push_front({ x - a, l }); }
        void push_back(i64 x, i64 l) { v.push_back({ x - a, l }); }
        bool empty() { return v.empty(); }
        i64 front() { return v.front().first + a; }
        std::pair<i64, i64> pop_front() {
          auto ret = v.front();
          v.pop_front();
          return { ret.first + a, ret.second };
        }
        std::pair<i64, i64> pop_back() {
          auto ret = v.back();
          v.pop_back();
          return { ret.first + a, ret.second };
        }
        void add(i64 x) { a += x; }
      };

      i64 min_pos = 0;
      i64 min_val = 0;
      aque m, r;
      r.push_back(1e13, 1e4);

      const auto shift = [&]() {
        auto [s, len] = m.pop_front();
        min_pos += len;
        min_val += s * len;
      };

      i64 prev = 0;
      for (const auto& [type, x] : vs) {
        const i64 dif = (x - prev);
        min_val += dif * (-min_pos);
        m.add(-dif);
        r.add(dif);

        while (!m.empty() && m.front() < 0) {
          shift();
        }

        if (type == 0) {
          min_pos -= 1;
          assert(!r.empty());
          auto [s, len] = r.pop_front();
          m.push_back(s, 1);
          if (len - 1 != 0) {
            r.push_front(s, len - 1);
          }
        }
        else {
          m.push_front(0, 1);
          i64 m_r = 1;
          while (m_r != 0) {
            assert(!m.empty());
            auto [s, len] = m.pop_back();
            const i64 t = std::min(len, m_r);
            r.push_front(s, t);
            m_r -= t;
            if (len - t != 0) {
              m.push_back(s, len - t);
            }
          }
        }
        prev = x;
      }

      while (!m.empty()) {
        shift();
      }

      return min_val;
    };

    int N, M, K;
    std::cin >> N >> M >> K;
    std::vector<int> B(N), R(M);
    for (auto& e : B) {
      std::cin >> e;
    }
    for (auto& e : R) {
      std::cin >> e;
    }

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

    std::map<int, std::pair<std::vector<int>, std::vector<int>>> map;
    for (const auto e : B) {
      map[e % K].first.push_back(e / K);
    }
    for (const auto e : R) {
      map[e % K].second.push_back(e / K);
    }

    long long ans = 0;
    for (auto& [key, val] : map) {
      auto& [l, r] = val;
      if (l.size() > r.size()) {
        std::cout << "-1\n";
        return;
      }
      ans += solve(l, r);
    }

    std::cout << ans << eoln;
  }

} // namespace n91

int main() {
  n91::main_();
  return 0;
}