/in/foo.cc: In function 'int main()':
/in/foo.cc:41:35: warning: suggest parentheses around '-' inside '<<' [-Wparentheses]
                 cnt=cnt|(a[j]<<n-j-1);
                                ~~~^~
/in/foo.cc:43:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
             for(int k=0; k<v1.size(); k++)
                          ~^~~~~~~~~~
/in/foo.cc:48:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
                 for(int j=0; j<v1.size(); j++)
                              ~^~~~~~~~~~