/in/foo.cc: In member function 'long long int func::calc(int)':
/in/foo.cc:28:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for(int p=1;p<a.size();++p)
                     ~^~~~~~~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:57:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i=0;i<res.size();++i)
                 ~^~~~~~~~~~~