/in/foo.cc: In member function 'long long int func::calc(int)':
/in/foo.cc:28:16: 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:57:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<res.size();++i)
              ~^~~~~~~~~~~
/in/foo.cc: In member function 'long long int func::calc(int)':
/in/foo.cc:27:6: warning: 'ret' is used uninitialized in this function [-Wuninitialized]
   ret+=a[0];