Language: C++

#if 0
????????£?????????????´?2??????
?????????????±?????????£????????´??¨?????´????????????????????¨????±?????????????
??????????????£??¨???????????????????????????
???????????????????????¨?????????????????????cross_product????????¨??????????????????????????????????????????dot_product????????¨???????????????
??????????????????????????¨??????????°???????????????????
?????´??¨?????´?????????????????¨????±?????????¨????????????????????¨?????????????????¢??°?????????????????????????????§????????????loop????????¨???????????????
?????´???loop??§????????´???loop??????????????????i--???i++??????????????????????????????????????????????????????
???????????????????????§???????????????????????????????????????
#endif
#include <complex>
#include <algorithm>
#include <cmath>
using namespace std;
typedef complex<int> xy_t;
int n=0;
xy_t point[100001];
xy_t ans[100001];


bool cmp(xy_t a,xy_t b)
{
  if(a.imag()<b.imag())
    return true;
  else if (a.imag()>b.imag())
    return false;
  else
    if(a.real()<b.real())
      return true;
    else
      return false;
}
bool cmp2(xy_t a,xy_t b)
{
  return !cmp(a,b);
}
int cross_product(xy_t a,xy_t b)
{
  return (conj(a)*b).imag();
}
bool legal(xy_t a, xy_t b, xy_t c)
{
  xy_t a1=b-a;
  xy_t a2=c-b;
  if(cross_product(a1,a2)>=0)
    return true;
  else
    return false;
}

int side()
{
  int cn=2;
  ans[0]=point[0];
  ans[1]=point[1];
  for(int i=2;i<n;i++)
  {
    if(legal(ans[cn-2],ans[cn-1],point[i]))
    {
      ans[cn++]=point[i];
    }
    else
    {
      if(cn>2)
      {
        cn--;
        i--;
      }
      else
      {
        ans[1]=point[i];
      }
    }
  }
  return cn;
}

int side2(int c)
{
  int cn=1+c;
  ans[c]=point[n-2];
  for(int i=n-3;i>=0;i--)
  {
    if(legal(ans[cn-2],ans[cn-1],point[i]))
    {
      ans[cn++]=point[i];
    }
    else
    {
      if(cn-c>1)
      {
        cn--;
        i++;
      }
      else
      {
        ans[c]=point[i];
      }
    }
  }
  return cn;
}
void printans(int countn)
{
  for(int i=0;i<countn;i++)
  {
    int x=ans[i].real();
    int y=ans[i].imag();
    cout << x << ' '<<y<<endl;
  }
}

int main()
{
  cin>>n;
  for(int i=0;i<n;i++)
  {
    int x,y;
    cin>>x>>y;
    point[i]=xy_t(x,y);
  }
  sort(point,point+n,cmp);
  int countn=side2(side())-1;
  cout<<countn<<endl;
  printans(countn);

/*  for(int i=0;i<n;i++)
  {
    int x=point[i].real();
    int y=point[i].imag();
    cout << x << ' '<<y<<endl;
  }*/

  return 0;
}

Compiler output:
a.cc:2:9: error: extended character £ is not valid in an identifier
    2 | ????????£?????????????´?2??????
      |         ^
a.cc:3:14: error: extended character ± is not valid in an identifier
    3 | ?????????????±?????????£????????´??¨?????´????????????????????¨????±?????????????
      |              ^
a.cc:3:24: error: extended character £ is not valid in an identifier
    3 | ?????????????±?????????£????????´??¨?????´????????????????????¨????±?????????????
      |                        ^
a.cc:3:68: error: extended character ± is not valid in an identifier
    3 | ?????????????±?????????£????????´??¨?????´????????????????????¨????±?????????????
      |                                                                    ^
a.cc:4:15: error: extended character £ is not valid in an identifier
    4 | ??????????????£??¨???????????????????????????
      |               ^
a.cc:6:38: error: extended character ° is not valid in an identifier
    6 | ??????????????????????????¨??????????°???????????????????
      |                                      ^
a.cc:7:38: error: extended character ± is not valid in an identifier
    7 | ?????´??¨?????´?????????????????¨????±?????????¨????????????????????¨?????????????????¢??°?????????????????????????????§????????????loop????????¨???????????????
      |                                      ^
a.cc:7:87: error: extended character ¢ is not valid in an identifier
    7 | ?????´??¨?????´?????????????????¨????±?????????¨????????????????????¨?????????????????¢??°?????????????????????????????§????????????loop????????¨???????????????
      |                                                                                       ^
a.cc:7:90: error: extended character ° is not valid in an identifier
    7 | ?????´??¨?????´?????????????????¨????±?????????¨????????????????????¨?????????????????¢??°?????????????????????????????§????????????loop????????¨???????????????
      |                                                                                          ^
a.cc:7:120: error: extended character § is not valid in an identifier
    7 | ?????´??¨?????´?????????????????¨????±?????????¨????????????????????¨?????????????????¢??°?????????????????????????????§????????????loop????????¨???????????????
      |                                                                                                                        ^
a.cc:8:16: error: extended character § is not valid in an identifier
    8 | ?????´???loop??§????????´???loop??????????????????i--???i++??????????????????????????????????????????????????????
      |                ^
a.cc:9:24: error: extended character § is not valid in an identifier
    9 | ???????????????????????§???????????????????????????????????????
      |                        ^
a.cc: In function 'void printans(int)':
a.cc:109:5: error: 'cout' was not declared in this scope
  109 |     cout << x << ' '<<y<<endl;
      |     ^~~~
a.cc:14:1: note: 'std::cout' is defined in header '<iostream>'; this is probably fixable by adding '#include <iostream>'
   13 | #include <cmath>
  +++ |+#include <iostream>
   14 | using namespace std;
a.cc: In function 'int main()':
a.cc:115:3: error: 'cin' was not declared in this scope
  115 |   cin>>n;
      |   ^~~
a.cc:115:3: note: 'std::cin' is defined in header '<iostream>'; this is probably fixable by adding '#include <iostream>'
a.cc:124:3: error: 'cout' was not declared in this scope
  124 |   cout<<countn<<endl;
      |   ^~~~
a.cc:124:3: note: 'std::cout' is defined in header '<iostream>'; this is probably fixable by adding '#include <iostream>'