/in/foo.cc: In function 'Iv Mul(Iv, int)':
/in/foo.cc:39:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i = 0;i<A.size() || t;i++)
                ~^~~~~~~~~
/in/foo.cc:41:7: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   if(i<A.size())
      ~^~~~~~~~~
/in/foo.cc: In function 'Iv sum(Iv, Iv)':
/in/foo.cc:53:9: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  while(i<A.size()||i<B.size()||t)
        ~^~~~~~~~~
/in/foo.cc:53:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  while(i<A.size()||i<B.size()||t)
                    ~^~~~~~~~~
/in/foo.cc:55:7: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   if(i<A.size()) t+= A[i];
      ~^~~~~~~~~
/in/foo.cc:56:7: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   if(i<B.size()) t+= B[i];
      ~^~~~~~~~~
/in/foo.cc: In function 'Iv Vsum(Iv, Iv)':
/in/foo.cc:19:44: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
 #define _for(i, a, b) for ( int i = (a); i < (b); ++i)
                                            ^
/in/foo.cc:66:2: note: in expansion of macro '_for'
  _for(i,0,B.size())
  ^~~~