12. The teacher is buying souvenirs for the students. There are three different types of souvenirs in the store (souvenirs of the same type are identical), priced at 1 yuan, 2 yuan, and 4 yuan respectively. The teacher plans to spend 101 yuan, and at least one of each type of souvenir must be purchased. There are $\qquad$ different purchasing schemes.
Let the number of souvenirs purchased at prices of 1 yuan, 2 yuan, and 4 yuan be $x, y, z$ respectively, then $x+2 y+4 z=101$. When $z=1$, $x+2 y=97, y=1,2, \cdots, 48 ;$ when $z=2$, $x+2 y=93, y=1,2, \cdots, 46$; when $z=3$, $x+2 y=89, y=1,2, \cdots, 44 ; \cdots,$ when $z=24$, $x+2 y=5, y=1,2$. Therefore, there are $2+4+\cdots+48=\frac{24 \times 50}{2}=600$ different purchasing schemes.