#include <bits/stdc++.h>
using std::vector;
using std::array;
using std::pair;
using std::tuple;
using i64 = std::int64_t;
struct Point {
int x, y;
Point(int x = 0, int y = 0) : x(x), y(y) {}
friend Point operator-(const Point& p, const Point& q) {
return Point(p.x - q.x, p.y - q.y);
}
friend i64 cross(const Point& p, const Point& q) {
return (i64)p.x * q.y - (i64)p.y * q.x;
}
};
struct Frac {
i64 x, y;
Frac(i64 x = 0, i64 y = 1) : x(x), y(y) {}
friend Frac operator+(const Frac& a, const Frac& b) {
return Frac(a.x * b.y + b.x * a.y, a.y * b.y);
}
friend Frac operator-(const Frac& a, const Frac& b) {
return Frac(a.x * b.y - b.x * a.y, a.y * b.y);
}
friend Frac operator*(const Frac& a, const Frac& b) {
return Frac(a.x * b.x, a.y * b.y);
}
friend bool operator<(const Frac& a, const Frac& b) {
return a.x * b.y < b.x * a.y;
}
};
int main() {
std::ios_base::sync_with_stdio(false);
std::cin.tie(nullptr);
int N, H;
std::cin >> N >> H;
vector<Point> P(N);
for (auto& [x, y] : P) {
std::cin >> x >> y;
}
vector<Point> pts;
vector<Frac> left(N), right(N);
for (int i = 1; i < N - 1; ++i) {
if (i % 2 == 1) {
int n = pts.size();
while (n >= 2) {
if (cross(P[i] - pts[n - 1], pts[n - 2] - pts[n - 1]) >= 0) {
pts.pop_back();
n -= 1;
} else {
break;
}
}
pts.push_back(P[i]);
} else {
int ok = 0, ng = pts.size();
while (ng - ok > 1) {
const int md = (ok + ng) / 2;
(cross(P[i] - pts[md], pts[md - 1] - pts[md]) < 0 ? ok : ng) = md;
}
left[i] = Frac(P[i].x) + Frac(pts[ok].x - P[i].x) * Frac(H - P[i].y, pts[ok].y - P[i].y);
}
}
pts.clear();
for (int i = N - 2; i >= 1; --i) {
if (i % 2 == 1) {
int n = pts.size();
while (n >= 2) {
if (cross(P[i] - pts[n - 1], pts[n - 2] - pts[n - 1]) <= 0) {
pts.pop_back();
n -= 1;
} else {
break;
}
}
pts.push_back(P[i]);
} else {
int ok = 0, ng = pts.size();
while (ng - ok > 1) {
const int md = (ok + ng) / 2;
(cross(P[i] - pts[md], pts[md - 1] - pts[md]) > 0 ? ok : ng) = md;
}
right[i] = Frac(P[i].x) + Frac(pts[ok].x - P[i].x) * Frac(H - P[i].y, pts[ok].y - P[i].y);
}
}
vector<pair<Frac, Frac>> interval;
for (int i = 2; i < N - 2; i += 2) {
interval.emplace_back(right[i], left[i]);
}
std::sort(interval.begin(), interval.end());
Frac last(-2000000000000);
int ans = 0;
for (const auto& [r, l] : interval) {
if (last < l) {
ans += 1;
last = r;
}
}
std::cout << ans << '\n';
return 0;
}
