/in/foo.cc: In function 'int main()':
/in/foo.cc:39:18: warning: unused variable 'n1' [-Wunused-variable]
  int x1,x2,y1,y2,n1,n2;
                  ^~
/in/foo.cc:39:21: warning: unused variable 'n2' [-Wunused-variable]
  int x1,x2,y1,y2,n1,n2;
                     ^~