#include "stdio.h"
int main(void)
{
float a,b,c;
scanf("%f\n",&a);
b=2*3.14*a;
printf("%f\n",b)
c=3.14*a^2;
printf("%f\n",c);
}

#include <stdio.h>
#include<stdlib.h>
#define pi 3.14
float ca(float x)
{
float z;
z=pi*2*x;
return(z);
}
float sa(float y)
{
float w;
w=pi*y*y;
return(w);
}
float main()
{
float r,c,s;
printf("输入半径；\n");
scanf("%f",&r);
c=ca(r);
s=sa(r);
printf("c=%f\ns=%f",c,s);
}