圆的周长

#include <stdio.h>
#define pi 3.1415926
int main()
{
	double r1=1.53,r2=21.83,r3=123.71,s1,s2,s3;
	
	s1=2*pi*r1;
	
	s2=2*pi*r2;
	
	s3=2*pi*r3;
	
	printf("s1=%10.2f\ns2=%10.2f\ns3=%10.2f\n",s1,s2,s3);
	
	return 0;
	
  }