foo.cc: In function ‘int main()’:
foo.cc:23:5: warning: variable ‘l’ set but not used [-Wunused-but-set-variable]
   23 | int l,r,d,t;
      |     ^
foo.cc:23:9: warning: unused variable ‘d’ [-Wunused-variable]
   23 | int l,r,d,t;
      |         ^
foo.cc:23:11: warning: unused variable ‘t’ [-Wunused-variable]
   23 | int l,r,d,t;
      |           ^