有手就行

#include<bits/stdc++.h>
using namespace std;
int main()
{
double a;
cin>>a;
double z=a2;
double c=a23.14159;
double s=aa3.14159;
cout<<fixed<<setprecision(4)<<z<<" "<<fixed<<setprecision(4)<<c<<" "<<fixed<<setprecision(4)<<s;
return 0;
}
//如果圆的半径是r，那么圆的直径、周长、面积分别是r2，r2PI，rrPI
//约定PI=3.14159csa