/in/foo.cc: In function 'int main()':
/in/foo.cc:6:2: error: expected ',' or ';' before 'double'
    6 |  double X1,Y1,X2,Y2;
      |  ^~~~~~
/in/foo.cc:7:13: error: 'X1' was not declared in this scope; did you mean 'y1'?
    7 |  while(cin>>X1>>Y1>>X2>>Y2){
      |             ^~
      |             y1
/in/foo.cc:7:17: error: 'Y1' was not declared in this scope; did you mean 'y1'?
    7 |  while(cin>>X1>>Y1>>X2>>Y2){
      |                 ^~
      |                 y1
/in/foo.cc:7:21: error: 'X2' was not declared in this scope
    7 |  while(cin>>X1>>Y1>>X2>>Y2){
      |                     ^~
/in/foo.cc:7:25: error: 'Y2' was not declared in this scope
    7 |  while(cin>>X1>>Y1>>X2>>Y2){
      |                         ^~
/in/foo.cc:12:8: error: expected ';' before '}' token
   12 |   set++
      |        ^
      |        ;
   13 |  }sort(a,a+set);
      |  ~