View Compilation Error

0_0_32241894_5022.cpp: In function 'int main()':
0_0_32241894_5022.cpp:20:104: error: 'y' was not declared in this scope
      y0= ((x3-x1)*(x2*x2-x1*x1 +y2*y2-y1*y1)+(x2-x1)*(x1*x1- x3*x3+y1*y1-y3*y3))/(2*(y2-y1)*(x3 -x1)-2*y -y1)*(x2-x1));
                                                                                                        ^