/in/foo.cc: In function 'int main()':
/in/foo.cc:19:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<a.length();i++)
              ~^~~~~~~~~~~
/in/foo.cc:32:54: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
  if(last=='1' || last=='4' || last=='9' || last=='6' && last=='5' || last=='0')
                                            ~~~~~~~~~~^~~~~~~~~~~~