import std.algorithm, std.conv, std.range, std.stdio, std.string; alias Point!int point; const maxX = 20000, maxY = 20000, gs = 20; auto grid = Grid!(point[], int)(maxX / gs + 1, maxY / gs + 1); void main() { auto n = readln.chomp.to!size_t; auto r = 0; foreach (_; 0..n) { auto rd = readln.split.to!(int[]), p = point(rd[0], rd[1]), gp = p / gs; if (!isOverlap(p, gp)) { grid[gp] ~= p; ++r; } } writeln(r); } auto isOverlap(point p, point gp) { foreach (q; grid.sibPoints8(gp).chain([gp])) foreach (tp; grid[q]) if ((p - tp).hypot2 < 400) return true; return false; } struct Point(T) { T x, y; pure auto opBinary(string op: "+")(Point!T rhs) const { return Point!T(x + rhs.x, y + rhs.y); } pure auto opBinary(string op: "-")(Point!T rhs) const { return Point!T(x - rhs.x, y - rhs.y); } pure auto opBinary(string op: "*")(Point!T rhs) const { return x * rhs.x + y * rhs.y; } pure auto opBinary(string op: "*")(T a) const { return Point!T(x * a, y * a); } pure auto opBinary(string op: "/")(T a) const { return Point!T(x / a, y / a); } pure auto hypot2() const { return x ^^ 2 + y ^^ 2; } } struct Grid(T, U) { import std.algorithm, std.conv, std.range, std.traits, std.typecons; const sibs4 = [Point!U(-1, 0), Point!U(0, -1), Point!U(1, 0), Point!U(0, 1)]; const sibs8 = [Point!U(-1, 0), Point!U(-1, -1), Point!U(0, -1), Point!U(1, -1), Point!U(1, 0), Point!U(1, 1), Point!U(0, 1), Point!U(-1, 1)]; T[][] m; const size_t rows, cols; mixin Proxy!m; this(size_t r, size_t c) { rows = r; cols = c; m = new T[][](rows, cols); } this(T[][] s) { rows = s.length; cols = s[0].length; m = s; } pure auto opIndex(Point!U p) const { return m[p.y][p.x]; } pure auto opIndex(size_t y) { return m[y]; } pure auto opIndex(size_t y, size_t x) const { return m[y][x]; } static if (isAssignable!T) { auto opIndexAssign(T v, Point!U p) { return m[p.y][p.x] = v; } auto opIndexAssign(T v, size_t y, size_t x) { return m[y][x] = v; } auto opIndexOpAssign(string op, V)(V v, Point!U p) { return mixin("m[p.y][p.x] " ~ op ~ "= v"); } auto opIndexOpAssign(string op, V)(V v, size_t y, size_t x) { return mixin("m[y][x] " ~ op ~ "= v"); } } pure auto validPoint(Point!U p) const { return p.x >= 0 && p.x < cols && p.y >= 0 && p.y < rows; } pure auto points() const { return rows.to!U.iota.map!(y => cols.to!U.iota.map!(x => Point!U(x, y))).joiner; } pure auto sibPoints4(Point!U p) const { return sibs4.map!(s => p + s).filter!(p => validPoint(p)); } pure auto sibPoints8(Point!U p) const { return sibs8.map!(s => p + s).filter!(p => validPoint(p)); } }