xA=input("xA = "); yA=input("yA = ");
xB=input("xB = "); yB=input("yB = ");
a=xB-xA;b=yB-yA;
xC=xB-b;yC=yB+a;
xD=xA-b;yD=yA+a;
disp("C:("+string(xC)+","+string(yC)+")");
disp("D:("+string(xD)+","+string(yD)+")");
