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#define x first
#define y second
#define pldld pair<long double, long double>
#define ld long double
#include <bits/stdc++.h>
using namespace std;
ifstream fin ("infasuratoare.in");
ofstream fout("infasuratoare.out");
const int N_MAX = 120000 + 5;
int n, k = 1;
pldld v[N_MAX], st[N_MAX];
bool cmp(pldld a, pldld b){
return (a < b);
}
ld deter (pldld a, pldld b, pldld c){
return (a.x*b.y + b.x*c.y + a.y*c.x - c.x*b.y - a.x*c.y - b.x*a.y);
}
int main(){
fin >> n;
for(int i = 1; i<=n; ++i)
fin >> v[i].x >> v[i].y;
sort(v+1,v+n+1,cmp);
st[1] = v[1];
k = 1;
for(int i = 2; i<=n; ++i){
while(k > 1 and deter(st[k-1], st[k], v[i]) > 0)
k --;
k ++;
st[k] = v[i];
}
for(int i = n-1; i>=1; --i){
while(k > 1 and deter(st[k-1], st[k], v[i]) > 0)
k --;
k ++;
st[k] = v[i];
}
k--;
fout << k << "\n";
for(int i = k; i>=1; --i)
fout << fixed << setprecision(6) << st[i].x << " " << st[i].y << '\n';
return 0;
}
//Andrei Muntean, 2018