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#include <bits/stdc++.h>
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using namespace std;
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const double PI = 3.14159265358979323846;
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class Shape {
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public:
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    // virtual function
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    virtual double getArea() = 0;
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};
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class Circle : public Shape {
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public:
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    double radius;
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    Circle(double r) {
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        radius = r;
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    }
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    double getArea() override {
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        return PI * radius;
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    }
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};
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class Rectangle : public Shape {
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public:
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    double width, height;
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    Rectangle(double w, double h) {
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        width = w;
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        height = h;
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    }
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    double getArea() override {
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        return width * height;
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    }
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};
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class Triangle : public Shape {
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public:
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    double a, b, c;
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    Triangle(double x, double y, double z) {
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        a = x;
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        b = y;
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        c = z;
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    }
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    double getArea() override {
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        double p = (a + b + c) / 2;
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        return sqrt(p * (p - a) * (p - b) * (p - c));
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    }
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};
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int main() {
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    Circle circle = Circle(1);
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    Rectangle rect = Rectangle(2, 5);
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    Triangle tr = Triangle(3, 4, 5);
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    cout << fixed << setprecision(3);
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    cout << circle.getArea() << " " << rect.getArea() << " " << tr.getArea() << endl;
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    return 0;
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}