A short message sent by a friend is a six-sentence, seven-character poem, each sentence is typed with one word, please help me guess!

Su Dongpo and Yuan are good friends of the same clan. One year, both of them were officials in Hangzhou. Yuan Gong Ji knew that Su Dongpo was an all-rounder and was good at couplets and riddles. Ordinary riddles can't beat him.

Once, they walked in the snow to enjoy the scenery. At this time, the snow on the road is more than an inch thick. Yuan Gong Ji said, "I have a mystery. I wonder if you can guess? " Su Dongpo-casually said: "It is also an elegant thing to enjoy snow guessing. Please come up with a riddle. "

Yuan said, "When the snow disappears, I will type a half sentence and seven words of Tang poetry."

Su Dongpo was secretly surprised. He thought, there is a truth in guessing half a poem, and half a sentence is a seven-character poem. Is it three or four words? Maybe three or four words are not, but half of seven words (vertical section), or three and a half words. However, although I am familiar with Tang poetry, I can't start at this time. At this time, they walked all the way to Longhong Temple. Suddenly, a flock of birds flew out of the Woods by the roadside and lined up to fly to the distant sky. Su Dongpo's heart lit up, thought it over carefully, smiled and nodded, secretly praising Yuan's half-sentence poem "Riddle" for being well written. However, he didn't want to tell the answer right away, and he also wanted to take this opportunity to embarrass Yuan. He pointed to the bird flying in the distance and said to Yuan, "Look at the scenery in the sky. Now I also ask you to guess two riddles. The riddle is' birds fly to heaven', and you can also type a half sentence of seven-character Tang poetry. "

Yuan didn't make sense at the moment, but he was still confused. Su Dongpo added, "You guess my riddle, and I guess yours." After a while, Su Dongpo leaned down and wrote a seven-character Tang poem in the snow: a line of egrets soared into the sky, scratched in the middle of the word "heron", and then said, "Your answer is the first half sentence-a line of white roads; My answer is the second part-birds fly into the sky. "