/in/foo.cc: In function 'int main()':
/in/foo.cc:41:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for(register int i = 0; i < f.size(); i++)
                                 ~~^~~~~~~~~~
/in/foo.cc:51:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for(register int i = 0; i < f.size(); i++)
                                 ~~^~~~~~~~~~
/in/foo.cc:36:9: warning: unused variable 'ans' [-Wunused-variable]
     int ans = -1, t = 0x7fffffff;
         ^~~