///*** Sown_Vipro ***///
/// ->TEAM SELECTION TEST<- ///
#include<bits/stdc++.h>
using namespace std;
//#pragma GCC optimize ("O3")
//#pragma GCC optimize ("unroll-loops")
//#pragma GCC target("popcnt")
#define F first
#define S second
#define pb push_back
#define pi pair<double, double>
#define pii pair<int, pair<int, int> >
#define FOR(i, a, b) for(int i = a; i <= b; ++i)
#define REP(i, a, b) for(int i = a; i >= b; --i)
#define all(s) s.begin(), s.end()
#define szz(s) int(s.size())
const string NAME = "sown";
const int N = 1e6 + 5, MAX = 1e6, MOD = 1e9 + 7;
void maxi(int &x, int y){ if(x < y) x = y; }
void mini(int &x, int y){ if(x > y) x = y; };
void add(int &x, int y){ x += y; x += MOD * (x < 0); x -= MOD * (x >= MOD); };
int n, h;
pi e[N];
pair<double, double> f(pi A, pi B){
double a = 1.0 * (1.0 * B.S - A.S) / (B.F - A.F);
double b = A.S - a * A.F;
return {a, b};
}
double g(pair<double, double> A, pair<double, double> B){
return 1.0 * (B.S - A.S) / (A.F - B.F);
}
void solve(){
cin >> n >> h;
FOR(i, 1, n){
cin >> e[i].F >> e[i].S;
}
double x = -1.0e18;
int res = 0;
for(int i = 3; i <= n - 2; i += 2){
pair<double, double> A = f(e[i - 1], e[i]);
pair<double, double> B = {0, h};
if(g(A, B) <= x) continue;
else{
++res;
A = f(e[i], e[i + 1]);
x = g(A, B);
}
// cout << x << "\n";
// cout << A.F << " " << A.S << " " << B.F << " " << B.S << " " << g(A, B) << "\n";
}
cout << res;
}
signed main(){
ios_base::sync_with_stdio(false);
cin.tie(0); cout.tie(0);
if(fopen((NAME + ".inp").c_str(), "r")){
freopen((NAME + ".inp").c_str(), "r", stdin);
freopen((NAME + ".out").c_str(), "w", stdout);
}
int t = 1;
// cin >> t;
while(t--){
solve();
}
}
