Convex Hull

using namespace std;
#include <vector>
#include <queue>
#include <algorithm>
#include <cmath>
#include <utility>
#include <bitset>
#include <set>
#include <string>
#include <iomanip>
#include <map>

#define pb push_back
#define pii pair<int,int>
#define F first
#define S second
#define LL long long
#define mid (LB+RB)/2
#define iter(x) x.begin(),x.end()

/*
8e7 so dian
FHVirus so dian
youou so dian
KYW so dian
hubert so dian
jass so dian
tingyu so dian
*/

//IO
#include <iostream>
#define theyRSOOOOOOOOODIAN ios_base::sync_with_stdio(false),cin.tie(0);
#define endl '\n'

//workspace

#define x first
#define y second
inline bool cross(pii o,pii a,pii b){
    return (a.x - o.x) * (b.y - o.y) <= (a.y - o.y) * (b.x - o.x);
}

struct stack{
    pii data[100100];
    int p = 0;
    inline void push(pii x){
        data[p++] = x;
    }
    inline pii top(){
        return data[p-1];
    }
    inline pii sectop(){
        return data[p-2];
    }
    inline bool pop(){
        if (p){
            --p;
            return 1;
        }
        return 0;
    }
    inline int unsigned size(){
        return p;
    }
};

int main(){
    theyRSOOOOOOOOODIAN
    int n;
    vector <pii> v;

    cin >> n;
    while (n--){
        int X,Y;

        cin >> X >> Y;
        v.pb({X,Y});
    }
    sort (iter(v));

    stack ch;
    for (auto i:v){
        while (ch.size() >= 2 && cross(ch.sectop(),ch.top(),i))
            ch.pop();

        ch.push(i);
    }

    for (int i=v.size()-2,lm=ch.size()+1;i>=0;--i){
        while (ch.size() >= lm && cross(ch.sectop(),ch.top(),v[i]))
            ch.pop();

        if (i)
            ch.push(v[i]);
    }

    cout << ch.size();

    return 0;
}