A386.圆的计算 题解

非常简单好吧~

#include <bits/stdc++.h>
using namespace std;
int main(){
	double r;
    cin >> r;
    printf("%.4f",r * 2);
    cout << " ";
    printf("%.4f",r * 2 * 3.14159);
    cout << " ";
    printf("%.4f",r * r * 3.14159);
    cout << " ";
	return 0;
}