If $f\left(x\right)$  is a monic polynomial of least degree such that  $f\left(1\right)=5,f\left(2\right)=4,f\left(3\right)=3,f\left(4\right)=2$   $f\left(5\right)=1then\left|f\left(0\right)\right|=\mathrm{...............}$ 

By condition we have  $f\left(x\right)=6-x$
1, 2, 3, 4, 5 are roots $\Rightarrow f\left(1\right)=5,F\left(2\right)=4$ 
 $f\left(3\right)=3,f\left(4\right)=2,f\left(5\right)=1$

$\begin{array}{l}\Rightarrow f\left(x\right)-(6-x)=0\\ \Rightarrow f\left(x\right)-(6-x)=(x-1)(x-2)(x-3)(x-4)(x-5)\\ putx=0\Rightarrow f\left(0\right)=(-1)(-2)(-3)(-4)(-5)\\ \Rightarrow f\left(0\right)=-120+6=-114\\ \left|f\left(0\right)\right|=114\end{array}$