/in/foo.cc: In function 'int main()':
/in/foo.cc:39:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i = 0 ; i < a.size()-1 ; i++){
                     ~~^~~~~~~~~~~~
/in/foo.cc:44:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
             if(i == a.size()-2)
                ~~^~~~~~~~~~~~~
/in/foo.cc:31:9: warning: unused variable 'p' [-Wunused-variable]
     int p = unique(a.begin(),a.end()) - a.begin();
         ^