The students were having a class on a cold morning in winter. The teacher (11) with his back to the fire. He wanted to give (12) to the students before he (13) his lesson. The teacher (14) to his students, "Before you speak, think. (15) fifty before you say anything important... a hundred if it is very important." At that time, the teacher’s coat tails caught fire, and the teacher didn’t know, but the students saw it at once. And they didn’t tell him about it.