Language: C++

#include "bits/stdc++.h"
using namespace std;
typedef long long LL;
typedef unsigned long long ULL;
typedef pair<int, int> P;
const LL MOD = 1000000007LL;
const double EPS = 1e-10;
struct Point {
	double x, y;
	Point(double x = 0, double y = 0) :x(x), y(y) {}
	Point operator+(Point &p) {
		return Point(x + p.x, y + p.y);
	}
	Point operator-(Point &p) {
		return Point(x - p.x, y - p.y);
	}
	Point operator*(double a) {
		return Point(x*a, y*a);
	}
	Point operator/(double a) {
		return Point(x / a, y / a);
	}
	double abs() {
		return sqrt(norm());
	}
	double norm() {
		return x*x + y*y;
	}
	bool operator<(const Point &p) const {
		return x != p.x ? x < p.x : y < p.y;
	}
	bool operator==(const Point &p) const {
		return fabs(x - p.x) < EPS && fabs(y - p.y) < EPS;
	}
};
typedef Point Vector;
struct Segment {
	Point p1, p2;
};
typedef Segment Line;
struct Circle {
	Point c;
	double r;
	Circle(Point c = Point(), double r = 0.0) :c(c), r(r) {}
};
typedef vector<Point> Polygon;
double norm(Vector a);
double abs(Vector a);
double dot(Vector a, Vector b);
double cross(Vector a, Vector b);
bool equals(double a, double b);
bool isOrthogonal(Vector a, Vector b);
bool isOrthogonal(Point a1, Point a2, Point b1, Point b2);
bool isOrthogonal(Segment s1, Segment s2);
bool isParallel(Vector a, Vector b);
bool isParallel(Point a1, Point a2, Point b1, Point b2);
bool isParallel(Segment s1, Segment s2);
Point project(Segment s, Point p);
Point reflect(Segment s, Point p);
int ccw(Point p0, Point p1, Point p2);
double getDistance(Point a, Point b);
double getDistanceLP(Line l, Point p);
double getDistanceSP(Segment s, Point p);
double getDistance(Segment s1, Segment s2);
bool intersect(Point p1, Point p2, Point p3, Point p4);
bool intersect(Segment s1, Segment s2);
bool intersect(Circle c, Line l);
bool intersect(Circle c1, Circle c2);
Point getCrossPoint(Segment s1, Segment s2);
pair<Point, Point> getCrossPoints(Circle c, Line l);
double arg(Vector p);
Vector polar(double a, double r);
pair<Point, Point> getCrossPoints(Circle c1, Circle c2);
double norm(Vector a) {
	return a.x*a.x + a.y*a.y;
}
double abs(Vector a) {
	return sqrt(norm(a));
}
double dot(Vector a, Vector b) {
	return a.x*b.x + a.y*b.y;
}
double cross(Vector a, Vector b) {
	return a.x*b.y - a.y*b.x;
}
bool equals(double a, double b) {
	return fabs(a - b) < EPS;
}
bool isOrthogonal(Vector a, Vector b) {
	return equals(dot(a, b), 0.0);
}
bool isOrthogonal(Point a1, Point a2, Point b1, Point b2) {
	return isOrthogonal(a1 - a2, b1 - b2);
}
bool isOrthogonal(Segment s1, Segment s2) {
	return equals(dot(s1.p2 - s1.p1, s2.p2 - s2.p1), 0.0);
}
bool isParallel(Vector a, Vector b) {
	return equals(cross(a, b), 0.0);
}
bool isParallel(Point a1, Point a2, Point b1, Point b2) {
	return isParallel(a1 - a2, b1 - b2);
}
bool isParallel(Segment s1, Segment s2) {
	return equals(cross(s1.p2 - s1.p1, s2.p2 - s2.p1), 0.0);
}
Point project(Segment s, Point p) {
	Vector base = s.p2 - s.p1;
	double r = dot(p - s.p1, base) / norm(base);
	return s.p1 + base*r;
}
Point reflect(Segment s, Point p) {
	return p + (project(s, p) - p)*2.0;
}
static const int COUNTER_CLOCKWISE = 1;
static const int CLOCKWISE = -1;
static const int ONLINE_BACK = 2;
static const int ONLINE_FRONT = -2;
static const int ON_SEGMENT = 0;
int ccw(Point p0, Point p1, Point p2) {
	Vector a = p1 - p0;
	Vector b = p2 - p0;
	if (cross(a, b) > EPS) return COUNTER_CLOCKWISE;
	if (cross(a, b) < -EPS) return CLOCKWISE;
	if (dot(a, b) < -EPS) return ONLINE_BACK;
	if (a.norm() < b.norm()) return ONLINE_FRONT;
	return ON_SEGMENT;
}
double getDistance(Point a, Point b) {
	return abs(a - b);
}
double getDistanceLP(Line l, Point p) {
	return abs(cross(l.p2 - l.p1, p - l.p1) / abs(l.p2 - l.p1));
}
double getDistanceSP(Segment s, Point p) {
	if (dot(s.p2 - s.p1, p - s.p1) < 0.0) return abs(p - s.p1);
	if (dot(s.p1 - s.p2, p - s.p2) < 0.0) return abs(p - s.p2);
	return getDistanceLP(s, p);
}
double getDistance(Segment s1, Segment s2) {
	if (intersect(s1, s2)) return 0.0;
	return min(min(getDistanceSP(s1, s2.p1), getDistanceSP(s1, s2.p2)), min(getDistanceSP(s2, s1.p1), getDistanceSP(s2, s1.p2)));
}
bool intersect(Point p1, Point p2, Point p3, Point p4) {
	return (ccw(p1, p2, p3)*ccw(p1, p2, p4) <= 0 && ccw(p3, p4, p1)*ccw(p3, p4, p2) <= 0);
}
bool intersect(Segment s1, Segment s2) {
	return intersect(s1.p1, s1.p2, s2.p1, s2.p2);
}
bool intersect(Circle c, Line l) {
	return getDistanceLP(l, c.c) <= c.r;
}
bool intersect(Circle c1, Circle c2) {
	return getDistance(c1.c, c2.c) <= c1.r + c2.r;
}
Point getCrossPoint(Segment s1, Segment s2) {
	Vector base = s2.p2 - s2.p1;
	double d1 = abs(cross(base, s1.p1 - s2.p1));
	double d2 = abs(cross(base, s1.p2 - s2.p1));
	double t = d1 / (d1 + d2);
	return s1.p1 + (s1.p2 - s1.p1)*t;
}
pair<Point, Point> getCrossPoints(Circle c, Line l) {
	assert(intersect(c, l));
	Vector pr = project(l, c.c);
	Vector e = (l.p2 - l.p1) / abs(l.p2 - l.p1);
	double base = sqrt(c.r*c.r - norm(pr - c.c));
	return make_pair(pr + e*base, pr - e*base);
}
double arg(Vector p) {
	return atan2(p.y, p.x);
}
Vector polar(double a, double r) {
	return Vector(cos(r)*a, sin(r)*a);
}
pair<Point, Point> getCrossPoints(Circle c1, Circle c2) {
	assert(intersect(c1, c2));
	double d = abs(c1.c - c2.c);
	double a = acos((c1.r*c1.r + d*d - c2.r*c2.r) / (2 * c1.r*d));
	double t = arg(c2.c - c1.c);
	return make_pair(c1.c + polar(c1.r, t + a), c1.c + polar(c1.r, t - a));
}
int main() {
	int N;
	while (cin >> N, N) {
		Point p[300];
		for (int i = 0; i < N; i++) {
			double x, y;
			cin >> x >> y;
			p[i] = Point(x, y);
		}
		int ans = 0;
		for (int i = 0; i < N; i++) {
			for (int j = i + 1; j < N; j++) {
				Vector d = p[j] - p[i];
				if (d.abs() > 2.0) continue;
				Point m = p[i] + d / 2.0;
				Vector r = Vector(-d.y, d.x);
				r = r / r.abs()*sqrt(1 - pow(d.abs() / 2.0, 2));
				Point p1 = m + r;
				Point p2 = m - r;
				int cnt1 = 0;
				int cnt2 = 0;
				for (int k = 0; k < N; k++) {
					if ((p[k] - p1).abs() <= 1) cnt1++;
					if ((p[k] - p2).abs() <= 1) cnt2++;
				}
				ans = max(ans, max(cnt1, cnt2));
			}
		}
		cout << ans << endl;
	}
}


Compiler output:
a.cc: In function 'Point project(Segment, Point)':
a.cc:110:21: error: no match for 'operator+' (operand types are 'Point' and 'Point')
  110 |         return s.p1 + base*r;
      |                ~~~~ ^ ~~~~~~
      |                  |        |
      |                  Point    Point
a.cc:11:15: note: candidate: 'Point Point::operator+(Point&)' (near match)
   11 |         Point operator+(Point &p) {
      |               ^~~~~~~~
a.cc:11:15: note:   conversion of argument 1 would be ill-formed:
a.cc:110:27: error: cannot bind non-const lvalue reference of type 'Point&' to an rvalue of type 'Point'
  110 |         return s.p1 + base*r;
      |                       ~~~~^~
In file included from /usr/include/c++/14/bits/stl_algobase.h:67,
                 from /usr/include/c++/14/algorithm:60,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:51,
                 from a.cc:1:
/usr/include/c++/14/bits/stl_iterator.h:627:5: note: candidate: 'template<class _Iterator> constexpr std::reverse_iterator<_Iterator> std::operator+(typename reverse_iterator<_Iterator>::difference_type, const reverse_iterator<_Iterator>&)'
  627 |     operator+(typename reverse_iterator<_Iterator>::difference_type __n,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:627:5: note:   template argument deduction/substitution failed:
a.cc:110:28: note:   'Point' is not derived from 'const std::reverse_iterator<_Iterator>'
  110 |         return s.p1 + base*r;
      |                            ^
/usr/include/c++/14/bits/stl_iterator.h:1798:5: note: candidate: 'template<class _Iterator> constexpr std::move_iterator<_IteratorL> std::operator+(typename move_iterator<_IteratorL>::difference_type, const move_iterator<_IteratorL>&)'
 1798 |     operator+(typename move_iterator<_Iterator>::difference_type __n,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1798:5: note:   template argument deduction/substitution failed:
a.cc:110:28: note:   'Point' is not derived from 'const std::move_iterator<_IteratorL>'
  110 |         return s.p1 + base*r;
      |                            ^
In file included from /usr/include/c++/14/string:54,
                 from /usr/include/c++/14/bitset:52,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:52:
/usr/include/c++/14/bits/basic_string.h:3598:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(const __cxx11::basic_string<_CharT, _Traits, _Allocator>&, const __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
 3598 |     operator+(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3598:5: note:   template argument deduction/substitution failed:
a.cc:110:28: note:   'Point' is not derived from 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
  110 |         return s.p1 + base*r;
      |                            ^
/usr/include/c++/14/bits/basic_string.h:3616:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(const _CharT*, const __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
 3616 |     operator+(const _CharT* __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3616:5: note:   template argument deduction/substitution failed:
a.cc:110:28: note:   mismatched types 'const _CharT*' and 'Point'
  110 |         return s.p1 + base*r;
      |                            ^
/usr/include/c++/14/bits/basic_string.h:3635:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(_CharT, const __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
 3635 |     operator+(_CharT __lhs, const basic_string<_CharT,_Traits,_Alloc>& __rhs)
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3635:5: note:   template argument deduction/substitution failed:
a.cc:110:28: note:   'Point' is not derived from 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
  110 |         return s.p1 + base*r;
      |                            ^
/usr/include/c++/14/bits/basic_string.h:3652:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(const __cxx11::basic_string<_CharT, _Traits, _Allocator>&, const _CharT*)'
 3652 |     operator+(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3652:5: note:   template argument deduction/substitution failed:
a.cc:110:28: note:   'Point' is not derived from 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
  110 |         return s.p1 + base*r;
      |                            ^
/usr/include/c++/14/bits/basic_string.h:3670:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(const __cxx11::basic_string<_CharT, _Traits, _Allocator>&, _CharT)'
 3670 |     operator+(const basic_string<_CharT, _Traits, _Alloc>& __lhs, _CharT __rhs)
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3670:5: note:   template argument deduction/substitution failed:
a.cc:110:28: note:   'Point' is not derived from 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
  110 |         return s.p1 + base*r;
      |                            ^
/usr/include/c++/14/bits/basic_string.h:3682:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(__cxx11::basic_string<_CharT, _Traits, _Allocator>&&, const __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
 3682 |     operator+(basic_string<_CharT, _Traits, _Alloc>&& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3682:5: note:   template argument deduction/substitution failed:
a.cc:110:28: note:   'Point' is not derived from 'std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
  110 |         return s.p1 + base*r;
      |                            ^
/usr/include/c++/14/bits/basic_string.h:3689:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(const __cxx11::basic_string<_CharT, _Traits, _Allocator>&, __cxx11::basic_string<_CharT, _Traits, _Allocator>&&)'
 3689 |     operator+(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3689:5: note:   template argument deduction/substitution failed:
a.cc:110:28: note:   'Point' is not derived from 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
  110 |         return s.p1 + base*r;
      |                            ^
/usr/include/c++/14/bits/basic_string.h:3696:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(__cxx11::basic_string<_CharT, _Traits, _Allocator>&&, __cxx11::basic_string<_CharT, _Traits, _Allocator>&&)'
 3696 |     operator+(basic_string<_CharT, _Traits, _Alloc>&& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3696:5: note:   template argument deduction/substitution failed:
a.cc:110:28: note:   'Point' is not derived from 'std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
  110 |         return s.p1 + base*r;
      |                            ^
/usr/include/c++/14/bits/basic_string.h:3719:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(const _CharT*, __cxx11::basic_string<_CharT, _Traits, _Allocator>&&)'
 3719 |     operator+(const _CharT* __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3719:5: note:   template argument deduction/substitution failed:
a.cc:110:28: note:   mismatched types 'const _CharT*' and 'Point'
  110 |         return s.p1 + base*r;
      |                            ^
/usr/include/c++/14/bits/basic_string.h:3726:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(_CharT, __cxx11::basic_string<_CharT, _Traits, _Allocator>&&)'
 3726 |     operator+(_CharT __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3726:5: note:   template argument deduction/substitution failed:
a.cc:110:28: note:   'Point' is not derived from 'std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
  110 |         return s.p1 + base*r;
      |                            ^
/usr/include/c++/14/bits/basic_string.h:3733:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(__cxx11::basic_string<_CharT, _Traits, _Allocator>&&, const _CharT*)'
 3733 |     operator+(basic_string<_CharT, _Traits, _Alloc>&& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3733:5: note:   template argument deduction/substitution failed:
a.cc:110:28: note:   'Point' is not derived from 'std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
  110 |         return s.p1 + base*r;
      |                            ^
/usr/include/c++/14/bits/basic_string.h:3740:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::__cxx11::basic_string<_CharT, _Traits, _Allocator> std::operator+(__cxx11::basic_string<_CharT, _Traits, _Allocator>&&, _CharT)'
 3740 |     operator+(basic_string<_CharT, _Traits, _Alloc>&& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3740:5: note:   template argument deduction/substitution failed:
a.cc:110:28: note:   'Point' is not derived from 'std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
  110 |         return s.p1 + base*r;
      |                            ^
In file included from /usr/include/c++/14/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:127:
/usr/include/c++/14/complex:340:5: note: candidate: 'template<class _Tp> std::comple