#include<stdio.h>
#include<math.h>
#define pi 3.14159265
int main()
{ int l,r;
  double result,angle;
  scanf("%d%d",&l,&r);
  if((double)l-sqrt(2)*r<1e-6)
    result=1.0;
  else if((double)l/2.0-(double)r>-1e-6)
    result=pi*r*r/(double)(l*l);
  else
  { angle=acos(l/2.0/r);
    result=((pi-4*angle)*r*r+2*l*r*sin(angle))/(double)(l*l);
  }
  printf("%.3lf\n",result*100.0);

  return 0;
}

SO DO I :
#include <stdio.h>
#include <math.h>

int main()
{
    double rect,r,piedeg,area=0,theta;
    scanf("%lf %lf",&rect,&r);
    if(rect>=(r*2)){
        printf("%.3lf",3.1415926535*r*r);
    }
    else if(((rect*sqrt(2))/2)<=r){
        printf("%.3lf",rect*rect);
    }
    else{
        rect=rect/2;
        theta=acos(rect/r);
        piedeg=(2*3.1415926535)-(8*theta);
        area=(piedeg*3.1415926535*r*r)/
(2*3.1415926535);
        area=area+(tan(theta)*rect*rect*4);
        printf("%.3lf",area);
    }
    return 0;
}




IT GOT CE , PLS HELP

sqrt(2)=>sqrt(2.0) ||sqrt((double) 2);