#include<iostream>
//#include<iomanip>
//#include<cmath>
float (*parea)(float);
float circle(float r);
float rect(float a,float b);
void main()
{
    using namespace std;
    float r=3.5,a=4,b=5;
    parea=circle;
    cout<<"半径为"<<r<<"的圆的面积为"<<parea(r)<<endl;
}
float circle(float r)
{
    return(3.14*r*r);
}