A group of 9 students, $s _ { 1 } , s _ { 2 } , \ldots , s _ { 9 }$, is to be divided to form three teams $X , Y$, and $Z$ of sizes 2,3 , and 4 , respectively. Suppose that $s _ { 1 }$ cannot be selected for the team $X$, and $s _ { 2 }$ cannot be selected for the team $Y$. Then the number of ways to form such teams, is $\_\_\_\_$ .