#include<iostream.h>
#include<math.h>

void main()
{
	long double x,a,b,e,h,A,M,s,p;
	int l,n,i,G,j;
	long double t[7]; 
	long double a1=7782.5,c1=972.5,b1=sqrt(a1*a1-c1*c1);
	a=0.0;
	b=3.14159263/2.0;
	e=0.00000001;
	h=b-a;
	t[0]=h*(sqrt((a1*sin(a))*(a1*sin(a))+(b1*cos(a))*(b1*cos(a)))+sqrt((a1*sin(b))*(a1*sin(b))+(b1*cos(b))*(b1*cos(b))))/2.0;
	l=0;
	n=1;
	do{
		A=t[0];
		M=0.0;
		for(i=0;i<n;i++){
			x=a+(i+0.5)*h;
			p=sqrt((a1*sin(x))*(a1*sin(x))+(b1*cos(x))*(b1*cos(x))); 
			M=M+p;
		}
		M=M*h;
		t[l+1]=(t[l]+M)/2.0;
		G=4;
		for(j=l;j>=0;j--){
			t[j]=(t[j+1]-1.0/G*t[j])/(1.0-1.0/G);
			G=4*G;
		}
		l=l+1;
		n=2*n;
		h=h/2.0;
		s=(t[0]-A)/t[0];
		if(s<0)
			s=-s;
	}while(s>e);
	cout<<4*t[0];
}