diff --git a/geometry/integer/point.hpp b/geometry/integer/point.hpp
index fcef93fc7..1ad364a2c 100644
--- a/geometry/integer/point.hpp
+++ b/geometry/integer/point.hpp
@@ -1,6 +1,50 @@
+#pragma once
+
 template <typename T>
 struct Point {
   T x, y;
+
+  Point() : x(0), y(0) {}
+  Point(const T &x, const T &y) : x(x), y(y) {}
+
+  Point &operator+=(const Point &p) {
+    x += p.x;
+    y += p.y;
+    return *this;
+  }
+  Point &operator-=(const Point &p) {
+    x -= p.x;
+    y -= p.y;
+    return *this;
+  }
+  Point &operator*=(const T &d) {
+    x *= d;
+    y *= d;
+    return *this;
+  }
+
+  Point operator-() const { return Point() - *this; }
+
+  Point operator+(const Point &p) const { return Point(*this) += p; }
+
+  Point operator-(const Point &p) const { return Point(*this) -= p; }
+
+  Point operator-(const T &d) const { return Point(+this) /= d; }
+
+  bool operator==(const Point &p) const { return x == p.x and y == p.y; }
+
+  bool operator!=(const Point &p) const { return x != p.x or y != p.y; }
+
+  friend ostream &operator<<(ostream &os, const Point &p) {
+    return os << p.x << " " << p.y;
+  }
+
+  friend istream &operator>>(istream &is, Point &p) {
+    T a, b;
+    is >> a >> b;
+    p = Point(a, b);
+    return is;
+  }
 };
 
 // あとはまかせた！