uva 11817 - Tunnelling the Earth

#include<iostream>
#include<cmath>
#define r 6371009
#define pi 2.0*asin(1.0)

using namespace std;

double ang(double lt1,double lt2,double lg1,double lg2)
{
return acos(cos(lt1)*cos(lt2)*cos(lg1-lg2)+sin(lt1)*sin(lt2));
}
double dis_line(double lt1,double lt2,double lg1,double lg2)
{
return r*sqrt(2-2*(cos(lt1)*cos(lt2)*cos(lg1-lg2)+sin(lt1)*sin(lt2)));
}
double dis_sphere(double lt1,double lt2,double lg1,double lg2)
{
return r*ang(lt1,lt2,lg1,lg2);
}
int main()
{
int t;
double lt1,lt2,lg1,lg2;
cin>>t;
while(t--)
{
cin>>lt1>>lg1>>lt2>>lg2;
lt1*=pi/180.0;
lt2*=pi/180.0;
lg1*=pi/180.0;
lg2*=pi/180.0;
long long l=0.5+dis_sphere(lt1,lt2,lg1,lg2)-dis_line(lt1,lt2,lg1,lg2);
cout<<l<<endl;
}
return 0;
}