/in/foo.cc: In function 'long long int bto10(long long int, long long int)':
/in/foo.cc:12:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i = 0;i < s.length();++i)
                   ~~^~~~~~~~~~~~
/in/foo.cc:10:9: warning: unused variable 'k' [-Wunused-variable]
     int k = s.length(), r = 0;
         ^
/in/foo.cc: In function 'long long int maxbit(long long int)':
/in/foo.cc:19:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i = 0;i < s.length();++i)
                   ~~^~~~~~~~~~~~