/in/foo.cc: In function 'int main()':
/in/foo.cc:27:6: warning: unused variable 'h1' [-Wunused-variable]
  int h1,m1,s1;
      ^~
/in/foo.cc:27:9: warning: unused variable 'm1' [-Wunused-variable]
  int h1,m1,s1;
         ^~
/in/foo.cc:27:12: warning: unused variable 's1' [-Wunused-variable]
  int h1,m1,s1;
            ^~
/in/foo.cc:28:6: warning: unused variable 'h2' [-Wunused-variable]
  int h2,m2,s2;
      ^~
/in/foo.cc:28:9: warning: unused variable 'm2' [-Wunused-variable]
  int h2,m2,s2;
         ^~
/in/foo.cc:28:12: warning: unused variable 's2' [-Wunused-variable]
  int h2,m2,s2;
            ^~