3. Let the function $f_{0}(x)=|x|, f_{1}(x)=\left|f_{0}(x)-1\right|, f_{2}(x)=\left|f_{1}(x)-2\right|$, then the area of the closed region formed by the graph of the function $y=f_{2}(x)$ and the $x$-axis is
7
3.【Analysis and Solution】Draw the graphs of the functions $y=f_{0}(x), y=f_{1}(x), y=f_{2}(x)$ in sequence (as shown in the figure). The required area is 7.