#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) -> i64 {
    if (lxt.empty()) {
      return 0;
    }
    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(1e10, 3e5);

    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;
}