code: public static <S extends Sequence<C>, C extends Compound> int getGCGChecksum(S sequence) {
  		String s = sequence.toString().toUpperCase();
  		int count = 0, check = 0;
  		for (int i = 0; i < s.length(); i++) {
  			count++;
  			check += count * s.charAt(i);
  			if (count == 57) {
  				count = 0;
  			}
  		}
  		return check % 10000;
  	}
docs: Calculates GCG checksum for a given sequence
  
  @param sequence given sequence
  @return GCG checksum