export const rotate = (op: string): string => {
  const length = op.length;
  if (length % 2 !== 0) {
    op = '0' + op;
  }
  if (op.length <= 2) {
    return op;
  }
  let rotatedString = '';
  for (let i = op.length - 1; i > 0; i -= 2) {
    rotatedString += op.charAt(i - 1) + op.charAt(i);
  }
  return rotatedString;
};