// <pwned> struct check{ bool operator()(char c){ return std::isalpha(c)|| std::isdigit(c); } };  std::string reduce_copy(std::string const &s){ std::string cpy; return std::remove_copy_if(s.begin(), s.end(), std::back_inserter(cpy), check()); }

std::string
reduceString(std::string const & s)
{
  std::string s2 = "";
  int len = s.size();
  int c;
  for ( int i = 0; i<len; i++ ) {
    c = s.at(i);
    if ( 65 <= c && c <= 90 ) { // UC
      c += 32;
      s2 += (char)c;
    } else if ( 97 <= c && c <= 122 ) { // LC
      s2 += (char)c;
    } else if ( 48 <= c && c <= 57 ) { // DIGIT
      s2 += (char)c;
    }
  }
  return s2;
}