Language: C++

include<bits/stdc++.h>
using namespace std;
#define INFS (1LL<<28)
#define INF (1LL<<60)
#define DEKAI 1000000007
#define lp(i,n) for(int i=0;i<n;i++)
#define int long long
#define double long double
#define all(n) n.begin(),n.end()
typedef complex<double> P;
 
vector<pair<double,pair<double,double>>> ans;
 
double rot(double x,double y){
	double angle=acos(x/(sqrt(x*x+y*y)));
	angle=angle*180.0/acos(-1);
	if(y<0)angle=360.0-angle;
	return angle;
}
 
signed main(){
	cout << fixed << setprecision(15);
	int n;
	cin>>n;
 
	lp(i,n){
		int x,y;
		cin>>x>>y;
		ans.push_back({arg(P(x,y)),{x,y}});
	}
	sort(ans.begin(),ans.end());
	lp(i,n){
		ans.push_back(ans[i]);
	}
	double r=0;
	lp(i,n){
		double sum[2]={0,0};
		for(int j=i;j<n+i;j++){
			sum[0]+=ans[j].second.first;
			sum[1]+=ans[j].second.second;
			r=max<double>(r,sqrt(sum[0]*sum[0]+sum[1]*sum[1]));
		}
	}
	cout<<r<<endl;
	return 0;
}

Compiler output:
a.cc:1:1: error: 'include' does not name a type
    1 | include<bits/stdc++.h>
      | ^~~~~~~
a.cc:10:9: error: 'complex' does not name a type
   10 | typedef complex<double> P;
      |         ^~~~~~~
a.cc:12:1: error: 'vector' does not name a type
   12 | vector<pair<double,pair<double,double>>> ans;
      | ^~~~~~
a.cc: In function 'long double rot(long double, long double)':
a.cc:15:30: error: 'sqrt' was not declared in this scope
   15 |         double angle=acos(x/(sqrt(x*x+y*y)));
      |                              ^~~~
a.cc:15:22: error: 'acos' was not declared in this scope
   15 |         double angle=acos(x/(sqrt(x*x+y*y)));
      |                      ^~~~
a.cc: In function 'int main()':
a.cc:22:9: error: 'cout' was not declared in this scope
   22 |         cout << fixed << setprecision(15);
      |         ^~~~
a.cc:22:17: error: 'fixed' was not declared in this scope
   22 |         cout << fixed << setprecision(15);
      |                 ^~~~~
a.cc:22:26: error: 'setprecision' was not declared in this scope
   22 |         cout << fixed << setprecision(15);
      |                          ^~~~~~~~~~~~
a.cc:24:9: error: 'cin' was not declared in this scope
   24 |         cin>>n;
      |         ^~~
a.cc:29:17: error: 'ans' was not declared in this scope
   29 |                 ans.push_back({arg(P(x,y)),{x,y}});
      |                 ^~~
a.cc:29:36: error: 'P' was not declared in this scope
   29 |                 ans.push_back({arg(P(x,y)),{x,y}});
      |                                    ^
a.cc:29:32: error: 'arg' was not declared in this scope
   29 |                 ans.push_back({arg(P(x,y)),{x,y}});
      |                                ^~~
a.cc:31:14: error: 'ans' was not declared in this scope
   31 |         sort(ans.begin(),ans.end());
      |              ^~~
a.cc:31:9: error: 'sort' was not declared in this scope; did you mean 'short'?
   31 |         sort(ans.begin(),ans.end());
      |         ^~~~
      |         short
a.cc:41:27: error: 'max' was not declared in this scope
   41 |                         r=max<double>(r,sqrt(sum[0]*sum[0]+sum[1]*sum[1]));
      |                           ^~~
a.cc:8:16: error: expected primary-expression before 'long'
    8 | #define double long double
      |                ^~~~
a.cc:41:31: note: in expansion of macro 'double'
   41 |                         r=max<double>(r,sqrt(sum[0]*sum[0]+sum[1]*sum[1]));
      |                               ^~~~~~
a.cc:44:18: error: 'endl' was not declared in this scope
   44 |         cout<<r<<endl;
      |                  ^~~~