#include<stdio.h>
#define PI 3.14
int main()
{
    float r, C, S;
    printf("please input r:");
    scanf("%f", &r);
    C = 2 * PI * r;   //周长公式
    S = PI * r * r;   //面积公式
    printf("C = %.2f\n", C);
    printf("S = %.2f\n", S);
    return 0;
}