/in/foo.cc: In function 'int main()':
/in/foo.cc:13:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int i = 0; i < a.size(); i ++)
                    ^
/in/foo.cc:17:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for(int j = t,k = 0;k < b.size();j ++,k ++ )
                          ^