/in/foo.cc: In function 'int main()':
/in/foo.cc:33:44: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
        (string(ptr->d_name).rfind(".out",l)==l-4||
         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~
/in/foo.cc:34:44: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         string(ptr->d_name).rfind(".ans",l)==l-4))
         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~