#include<stdio.h>
#include<stdlib.h>
#include<math.h>
#define pi 2*acos(0)
struct Point2D
{
double x,y;
Point2D(double x_pos=0,double y_pos=0){
x = x_pos;y=y_pos;
}
double Distance(Point2D B){
return sqrt((x-B.x)*(x-B.y)+(y-B.y)*(y-B.y));
}
};
struct Circle
{
Point2D center;
double radius;
Circle(double x_pos,double y_pos, double r){
center.x=x_pos;
center.y=y_pos;
radius = r;
}
double Area(){
return pi*radius*radius;
}
};
int main(){
Circle c = Circle(0,0,6);
printf("%lf\n",c.Area());
return 0;
}
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