foo.cc: In function ‘int main()’:
foo.cc:20:13: warning: unused variable ‘front’ [-Wunused-variable]
   20 |         int front=1,back=1,x=1,y=1;
      |             ^~~~~
foo.cc:20:21: warning: unused variable ‘back’ [-Wunused-variable]
   20 |         int front=1,back=1,x=1,y=1;
      |                     ^~~~
foo.cc:20:28: warning: unused variable ‘x’ [-Wunused-variable]
   20 |         int front=1,back=1,x=1,y=1;
      |                            ^
foo.cc:20:32: warning: unused variable ‘y’ [-Wunused-variable]
   20 |         int front=1,back=1,x=1,y=1;
      |                                ^