while 1:a,b,c,d,e,f,g,h=map(float,raw_input().split());c-=a;e-=a;d-=b;f-=b;t=(e*e-c*e+f*f-d*f)/(c*f-d*e);q=c-d*t;d+=c*t;print+(q*q+d*d>(q-g*2+a*2)**2+(d-h*2+b*2)**2)