#include <cassert>
#include <cmath>
#include <cstdint>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <functional>
#include <iostream>
#include <limits>
#include <map>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <sstream>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

using namespace std;

using Int = long long;

template <class T1, class T2> ostream &operator<<(ostream &os, const pair<T1, T2> &a) { return os << "(" << a.first << ", " << a.second << ")"; };
template <class T> ostream &operator<<(ostream &os, const vector<T> &as) { const int sz = as.size(); os << "["; for (int i = 0; i < sz; ++i) { if (i >= 256) { os << ", ..."; break; } if (i > 0) { os << ", "; } os << as[i]; } return os << "]"; }
template <class T> void pv(T a, T b) { for (T i = a; i != b; ++i) cerr << *i << " "; cerr << endl; }
template <class T> bool chmin(T &t, const T &f) { if (t > f) { t = f; return true; } return false; }
template <class T> bool chmax(T &t, const T &f) { if (t < f) { t = f; return true; } return false; }
#define COLOR(s) ("\x1b[" s "m")

////////////////////////////////////////////////////////////////////////////////
template <unsigned M_> struct ModInt {
  static constexpr unsigned M = M_;
  unsigned x;
  constexpr ModInt() : x(0U) {}
  constexpr ModInt(unsigned x_) : x(x_ % M) {}
  constexpr ModInt(unsigned long long x_) : x(x_ % M) {}
  constexpr ModInt(int x_) : x(((x_ %= static_cast<int>(M)) < 0) ? (x_ + static_cast<int>(M)) : x_) {}
  constexpr ModInt(long long x_) : x(((x_ %= static_cast<long long>(M)) < 0) ? (x_ + static_cast<long long>(M)) : x_) {}
  ModInt &operator+=(const ModInt &a) { x = ((x += a.x) >= M) ? (x - M) : x; return *this; }
  ModInt &operator-=(const ModInt &a) { x = ((x -= a.x) >= M) ? (x + M) : x; return *this; }
  ModInt &operator*=(const ModInt &a) { x = (static_cast<unsigned long long>(x) * a.x) % M; return *this; }
  ModInt &operator/=(const ModInt &a) { return (*this *= a.inv()); }
  ModInt pow(long long e) const {
    if (e < 0) return inv().pow(-e);
    ModInt a = *this, b = 1U; for (; e; e >>= 1) { if (e & 1) b *= a; a *= a; } return b;
  }
  ModInt inv() const {
    unsigned a = M, b = x; int y = 0, z = 1;
    for (; b; ) { const unsigned q = a / b; const unsigned c = a - q * b; a = b; b = c; const int w = y - static_cast<int>(q) * z; y = z; z = w; }
    assert(a == 1U); return ModInt(y);
  }
  ModInt operator+() const { return *this; }
  ModInt operator-() const { ModInt a; a.x = x ? (M - x) : 0U; return a; }
  ModInt operator+(const ModInt &a) const { return (ModInt(*this) += a); }
  ModInt operator-(const ModInt &a) const { return (ModInt(*this) -= a); }
  ModInt operator*(const ModInt &a) const { return (ModInt(*this) *= a); }
  ModInt operator/(const ModInt &a) const { return (ModInt(*this) /= a); }
  template <class T> friend ModInt operator+(T a, const ModInt &b) { return (ModInt(a) += b); }
  template <class T> friend ModInt operator-(T a, const ModInt &b) { return (ModInt(a) -= b); }
  template <class T> friend ModInt operator*(T a, const ModInt &b) { return (ModInt(a) *= b); }
  template <class T> friend ModInt operator/(T a, const ModInt &b) { return (ModInt(a) /= b); }
  explicit operator bool() const { return x; }
  bool operator==(const ModInt &a) const { return (x == a.x); }
  bool operator!=(const ModInt &a) const { return (x != a.x); }
  friend std::ostream &operator<<(std::ostream &os, const ModInt &a) { return os << a.x; }
};
////////////////////////////////////////////////////////////////////////////////

constexpr unsigned MO = 998244353;
using Mint = ModInt<MO>;

/*
  b[i] := a[i] + i(i-1)/2
  2 a[i] > a[i-1] + a[i+1]
  2 b[i] >= b[i-1] + b[i+1]
*/

using Pt = pair<Int, Int>;
bool cw(const Pt &a, const Pt &b, const Pt &c) {
  return ((__int128)(b.first - a.first) * (c.second - a.second) < (__int128)(b.second - a.second) * (c.first - a.first));
}

// \sum[0<=x<n] (a + d x)
Mint calc(Int n, Mint a, Mint d) {
  Mint ret = 0;
  ret += a * n;
  ret += d * (Mint(n) * Mint(n - 1) / 2);
  return ret;
}

int N;
Int M;
vector<Int> X, Y;

int main() {
  for (; ~scanf("%d%lld", &N, &M); ) {
    X.resize(N + 2);
    Y.resize(N + 2);
    X[0] = 0;
    Y[0] = 0;
    for (int i = 1; i <= N; ++i) {
      scanf("%lld%lld", &X[i], &Y[i]);
    }
    X[N + 1] = M;
    Y[N + 1] = 0;
    
    for (int i = 0; i <= N + 1; ++i) {
      Y[i] += X[i] * (X[i] - 1) / 2;
    }
    
    vector<Pt> ps;
    for (int i = 0; i <= N + 1; ++i) {
      const Pt p(X[i], Y[i]);
      for (; ps.size() >= 2 && !cw(ps.end()[-2], ps.end()[-1], p); ps.pop_back()) {}
      ps.push_back(p);
    }
// cerr<<"ps = "<<ps<<endl;
    
    Mint ans = 0;
    for (int j = 0; j < (int)ps.size() - 1; ++j) {
      const Pt &p0 = ps[j];
      const Pt &p1 = ps[j + 1];
      const Int dx = p1.first - p0.first;
      const Int dy = p1.second - p0.second;
      Int r = dy % dx;
      if (r < 0) r += dx;
      const Int q = (dy - r) / dx;
// cerr<<p0<<" "<<p1<<" "<<q<<" "<<r<<endl;
      // q+1, ..., q+1, q, ..., q
      ans += calc(r, p0.second, q + 1);
      ans += calc(dx - r, p0.second + r * (q + 1), q);
    }
    // \sum[0<=x<M] x(x-1)/2
    ans -= Mint(M) * Mint(M - 1) * Mint(M - 2) / 6;
    printf("%u\n", ans.x);
  }
  return 0;
}