/in/foo.cc: In function 'std::vector<int> mul(std::vector<int>&, int)':
/in/foo.cc:11:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i = 0; i < A.size() || t; i ++ )
                      ^
/in/foo.cc:13:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         if(i < A.size()) t += A[i] * b;
              ^