Once upon a time, there was a boy named Mark. He loved to build with his toy blocks. One day, he wanted to build a big tower. He thought it would be easy.
But, his little sister wanted to play too. She tried to help Mark build the tower. But she was too little, and the blocks fell down. Mark was sad and mad.
Mark and his sister tried again. They worked together to build the tower. This time, it was not easy. But, they did it! They were happy and hugged each other.
