/in/foo.cc: In function 'int main()':
/in/foo.cc:12:6: warning: unused variable 'i' [-Wunused-variable]
  int i = 0;
      ^
/in/foo.cc:13:6: warning: unused variable 'len' [-Wunused-variable]
  int len = STR.length();
      ^~~
/in/foo.cc:14:6: warning: unused variable 'x' [-Wunused-variable]
  int x = 0, y = 0;
      ^
/in/foo.cc:14:13: warning: unused variable 'y' [-Wunused-variable]
  int x = 0, y = 0;
             ^