#include <bits/stdc++.h>

using namespace std;

using int64 = long long;
// const int mod = 1e9 + 7;
const int mod = 998244353;

const int64 infll = (1LL << 62) - 1;
const int inf = (1 << 30) - 1;

struct IoSetup {
  IoSetup() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(10);
    cerr << fixed << setprecision(10);
  }
} iosetup;


template< typename T1, typename T2 >
ostream &operator<<(ostream &os, const pair< T1, T2 > &p) {
  os << p.first << " " << p.second;
  return os;
}

template< typename T1, typename T2 >
istream &operator>>(istream &is, pair< T1, T2 > &p) {
  is >> p.first >> p.second;
  return is;
}

template< typename T >
ostream &operator<<(ostream &os, const vector< T > &v) {
  for(int i = 0; i < (int) v.size(); i++) {
    os << v[i] << (i + 1 != v.size() ? " " : "");
  }
  return os;
}

template< typename T >
istream &operator>>(istream &is, vector< T > &v) {
  for(T &in : v) is >> in;
  return is;
}

template< typename T1, typename T2 >
inline bool chmax(T1 &a, T2 b) { return a < b && (a = b, true); }

template< typename T1, typename T2 >
inline bool chmin(T1 &a, T2 b) { return a > b && (a = b, true); }

template< typename T = int64 >
vector< T > make_v(size_t a) {
  return vector< T >(a);
}

template< typename T, typename... Ts >
auto make_v(size_t a, Ts... ts) {
  return vector< decltype(make_v< T >(ts...)) >(a, make_v< T >(ts...));
}

template< typename T, typename V >
typename enable_if< is_class< T >::value == 0 >::type fill_v(T &t, const V &v) {
  t = v;
}

template< typename T, typename V >
typename enable_if< is_class< T >::value != 0 >::type fill_v(T &t, const V &v) {
  for(auto &e : t) fill_v(e, v);
}

template< typename F >
struct FixPoint : F {
  FixPoint(F &&f) : F(forward< F >(f)) {}

  template< typename... Args >
  decltype(auto) operator()(Args &&... args) const {
    return F::operator()(*this, forward< Args >(args)...);
  }
};

template< typename F >
inline decltype(auto) MFP(F &&f) {
  return FixPoint< F >{forward< F >(f)};
}

/**
 * @brief Dynamic-Li-Chao-Tree
 * @docs docs/dynamic-li-chao-tree.md
*/
template< typename T, T x_low, T x_high, T id >
struct DynamicLiChaoTree {

  struct Line {
    T a, b;

    Line(T a, T b) : a(a), b(b) {}

    inline T get(T x) const { return a * x + b; }
  };

  struct Node {
    Line x;
    Node *l, *r;

    Node(const Line &x) : x{x}, l{nullptr}, r{nullptr} {}
  };

  Node *root;

  DynamicLiChaoTree() : root{nullptr} {}

  Node *add_line(Node *t, Line &x, const T &l, const T &r, const T &x_l, const T &x_r) {
    if(!t) return new Node(x);

    T t_l = t->x.get(l), t_r = t->x.get(r);

    if(t_l <= x_l && t_r <= x_r) {
      return t;
    } else if(t_l >= x_l && t_r >= x_r) {
      t->x = x;
      return t;
    } else {
      T m = (l + r) / 2;
      if(m == r) --m;
      T t_m = t->x.get(m), x_m = x.get(m);
      if(t_m > x_m) {
        swap(t->x, x);
        if(x_l >= t_l) t->l = add_line(t->l, x, l, m, t_l, t_m);
        else t->r = add_line(t->r, x, m + 1, r, t_m + x.a, t_r);
      } else {
        if(t_l >= x_l) t->l = add_line(t->l, x, l, m, x_l, x_m);
        else t->r = add_line(t->r, x, m + 1, r, x_m + x.a, x_r);
      }
      return t;
    }
  }

  void add_line(const T &a, const T &b) {
    Line x(a, b);
    root = add_line(root, x, x_low, x_high, x.get(x_low), x.get(x_high));
  }

  Node *add_segment(Node *t, Line &x, const T &a, const T &b, const T &l, const T &r, const T &x_l, const T &x_r) {
    if(r < a || b < l) return t;
    if(a <= l && r <= b) {
      Line y{x};
      return add_line(t, y, l, r, x_l, x_r);
    }
    if(t) {
      T t_l = t->x.get(l), t_r = t->x.get(r);
      if(t_l <= x_l && t_r <= x_r) return t;
    } else {
      t = new Node(Line(0, id));
    }
    T m = (l + r) / 2;
    if(m == r) --m;
    T x_m = x.get(m);
    t->l = add_segment(t->l, x, a, b, l, m, x_l, x_m);
    t->r = add_segment(t->r, x, a, b, m + 1, r, x_m + x.a, x_r);
    return t;
  }

  void add_segment(const T &l, const T &r, const T &a, const T &b) {
    Line x(a, b);
    root = add_segment(root, x, l, r - 1, x_low, x_high, x.get(x_low), x.get(x_high));
  }

  T query(const Node *t, const T &l, const T &r, const T &x) const {
    if(!t) return id;
    if(l == r) return t->x.get(x);
    T m = (l + r) / 2;
    if(m == r) --m;
    if(x <= m) return min(t->x.get(x), query(t->l, l, m, x));
    else return min(t->x.get(x), query(t->r, m + 1, r, x));
  }

  T query(const T &x) const {
    return query(root, x_low, x_high, x);
  }
};

int main() {
  int N, C;
  cin >> N >> C;
  vector< int64 > A(N), B(N);
  for(int i = 0; i < N; i++) {
    cin >> A[i] >> B[i];
  }
  vector< int64 > dp(N + 1, infll);
  dp[0] = 0;
  vector< int64 > dp2(N + 1, infll);
  dp2[0] = 0;

  DynamicLiChaoTree< int64, 0LL, 1100000000000LL, infll > latte;
  DynamicLiChaoTree< int64, 0LL, 200000LL, infll > malta;


  auto set_j = [&](int64 j, int64 v) {
    v += j * j * C;
    v += j * C;
    chmin(dp2[j], v);
  };

  auto get_j = [&](int64 j) {
    return malta.query(j) + j * j * C + j * C;
  };
  for(int64 i = 1; i <= N; i++) {
    int64 ret = infll;


    if(chmin(dp[i], get_j(i))) {
      set_j(i, dp[i]);
    }
    for(int64 j = 0; j < i; j++) {
      chmin(ret, dp2[j] + -(2 * j * (A[i - 1] + i * C)));
    }
    ret += i * i * C;
    ret -= i * C;
    ret += i * A[i - 1] * 2;
    ret /= 2;
    ret += B[i - 1];
    ret *= 2;
    ret += i * i * C;
    ret -= i * C;
    ret -= i * A[i - 1] * 2;

    malta.add_line(A[i - 1] * 2 - 2 * i * C, ret);
    /*
    for(int64 j = i; j <= N; j++) {
      if(chmin(dp[j], ret + j * (A[i - 1] * 2 - 2 * i * C) + j * j * C + j * C)) {
        set_j(j, dp[j]);
      }
    }
     */
  }
  cout << dp[N] / 2 << "\n";
}