docs: static private void append(StringBuilder tgt, String pfx, int dgt, long val) {
  		tgt.append(pfx);
  		if (dgt > 1) {
  			int pad = (dgt - 1);
  			for (long xa = val; xa > 9 && pad > 0; xa /= 10) {
  				pad--;
  			}
  			for (int xa = 0; xa < pad; xa++) {
  				tgt.append('0');
  			}
  		}
  		tgt.append(val);
  	}