/*DavitMarg*/
#include <iostream>
#include <algorithm>
#include <cmath>
#include <vector>
#include <string>
#include <cstring>
#include <map>
#include <set>
#include <queue>
#include <iomanip>
#include <stack>
#include <cassert>
#include <iterator>
#include <bitset>
#include <fstream>
#define death
#ifndef death
#include<trilib.h>
#endif // death
#define mod 1000000007ll
#define LL long long
#define LD long double
#define MP make_pair
#define PB push_back
#define all(v) v.begin(),v.end()
using namespace std;
#ifdef death
int get_n()
{
int x;
cin >> x;
return x;
}
vector<pair<LL, LL>> point;
bool is_clockwise(int a, int b, int c)
{
}
void give_answer(int x)
{
cout << x << endl;
}
#endif // death
map<pair<int, pair<int, int>>, bool> used, pre;
bool cw(int a, int b, int c)
{
pair<LL, LL> A, B, C;
A = point[a];
B = point[b];
C = point[c];
return A.first * (B.second - C.second) + B.first * (C.second - A.second) + C.first * (A.second - B.second) < 0;
}
bool ccw(int a, int b, int c)
{
pair<LL, LL> A, B, C;
A = point[a];
B = point[b];
C = point[c];
return A.first * (B.second - C.second) + B.first * (C.second - A.second) + C.first * (A.second - B.second) > 0;
}
int ans, n;
vector<int> p;
int convex(vector<int> p)
{
vector<int> up, down;
int st, en;
st = p[0];
en = p.back();
sort(all(p), [](int a, int b) {
if (point[a].first != point[b].first)
return point[a].first < point[b].first;
return point[a].second < point[b].second;
});
up.PB(p[0]);
down.PB(p[0]);
for (int i = 1; i < p.size(); i++)
{
if (i == p.size() - 1 || cw(st, p[i], en))
{
while (up.size() > 1 && !cw(up[up.size() - 2], up[up.size() - 1], p[i]))
up.pop_back();
up.PB(p[i]);
}
if (i == p.size() - 1 || ccw(st, p[i], en))
{
while (down.size() > 1 && !ccw(down[down.size() - 2], down[down.size() - 1], p[i]))
down.pop_back();
down.PB(p[i]);
}
}
down.pop_back();
reverse(all(down));
down.pop_back();
reverse(all(down));
while (!down.empty())
{
up.PB(down.back());
down.pop_back();
}
return up.size();
}
int main()
{
n = get_n();
#ifdef death
point.PB(MP(0, 0));
for (int i = 0; i < n; i++)
{
LL x, y;
cin >> x >> y;
point.PB(MP(x, y));
}
#endif // death
for (int i = 0; i < n; i++)
p.PB(i + 1);
random_shuffle(all(p));
ans = convex(p);
give_answer(ans);
return 0;
}
/*
4
5 10
0 0
4 3
10 0
*/
