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input/code.cpp: In function 'long long int ibm(long double)':
input/code.cpp:61:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int i=0; i<xs.size(); ++i){
                           ^
input/code.cpp:65:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int i=0; i<pts.size(); ++i){
                            ^

#include <iostream>
#include <iomanip>
#include <vector>
#include <algorithm>
#include <cmath>
#include <unordered_map>
#define MP make_pair
#define F first
#define S second
#define SZ (1<<18)
using namespace std;
int n;

long double cot(long double a){
  long double d=tan(a);
  if (d!=d) return 0;
  else return 1l/d;
}

int sp[SZ];

void put(int a){a+=SZ/2;
  sp[a]+=1;
  for (a/=2; a; a/=2) sp[a]=sp[2*a]+sp[2*a+1];
}

int get(int a, int b){a+=SZ/2; b+=SZ/2;
  int rv=0;
  while (a<b){
    if (a%2==1) rv+=sp[a++];
    if (b%2==0) rv+=sp[b--];
    a/=2; b/=2;
  }if (a==b) rv+=sp[a];
  return rv;
}


long double PI=-1;


int x[101010];
int y[101010];

vector<pair<pair<long double, long double>, int> > pts;

vector<long double> xs;
unordered_map<long double, int> ix;

long long ibm(long double ang){
  for (int i=0; i<SZ; ++i) sp[i]=0;
  xs.clear();
  long double k=cot(ang);
  for (int i=0; i<n; ++i){
    long double xc=x[pts[i].S];
    xc-=k*pts[i].F.F;
    xs.push_back(xc);
    pts[i].F.S=xc;
  }
  sort(xs.begin(), xs.end());
  
  for (int i=0; i<xs.size(); ++i){
    ix[xs[i]]=i;
  }
  long long sm=0;
  for (int i=0; i<pts.size(); ++i){
    int ii=ix[pts[i].F.S];
    int ca=get(0, ii);
    sm+=ca;
    put(ii);
  }
  return sm;
}


long double bin(long long v){
  long double a=0;
  long double b=PI;
  for (int i=0; i<35; ++i){
    long double m=(a+b)/2;
    if (ibm(m)>=v) b=m;
    else a=m;
  }
  return (a+b)/2;
}

int main(){
  PI=acos(PI);
  ios_base::sync_with_stdio(0); cin.tie(0);
  cin >> n;
  for (int i=0; i<n; ++i) cin >> x[i] >> y[i];
  for (int i=0; i<n; ++i) pts.push_back(MP(MP(y[i], x[i]), i));
  sort(pts.begin(), pts.end());
  long double a=bin(((long long)n*(n-1)/2+1)/2);
  long double b=bin(((long long)n*(n-1)/2+2)/2);
  cout << setprecision(20) << (a+b)/2 << "\n";
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED

Test 13

Verdict: ACCEPTED

Test 14

Verdict: ACCEPTED

Test 15

Verdict: ACCEPTED

Test 16

Verdict: ACCEPTED

Test 17

Verdict: ACCEPTED

Test 18

Verdict: ACCEPTED

Test 19

Verdict: ACCEPTED

Test 20

Verdict: TIME LIMIT EXCEEDED

Test 21

Verdict: TIME LIMIT EXCEEDED

Test 22

Verdict: ACCEPTED

Test 23

Verdict: ACCEPTED

Test 24

Verdict: ACCEPTED

Test 25

Verdict: ACCEPTED

Test 26

Verdict: ACCEPTED

Test 27

Verdict: ACCEPTED

Test 28

Verdict: TIME LIMIT EXCEEDED

Test 29

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Test 30

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Test 31

Verdict: TIME LIMIT EXCEEDED

Test 32

Verdict: ACCEPTED

Test 33

Verdict: ACCEPTED

Test 34

Verdict: TIME LIMIT EXCEEDED

Test 35

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Test 36

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Test 37

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Test 38

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Test 39

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Test 40

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Test 41

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Test 42

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Test 43

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Test 44

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Test 45

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Test 46

Verdict: TIME LIMIT EXCEEDED

Test 47

Verdict: TIME LIMIT EXCEEDED

Test 48

Verdict: ACCEPTED

Test 49

Verdict: ACCEPTED