Match the functons with their graphs. Enter the letter of the graph below which corresponds to the function.

 1. Piecewise function: $f(x)=1$ if $x\le 1$, and $f(x)=x+1$ if $x> 1$
 2. Piecewise function: $f(x)=3$ if $x<2$, and $f(x)=x-1$ if $x\ge 2$
 3. Piecewise function: $f(x)=2$ if $x\le -1$, and $f(x)=x^2$ if $x>-1$
 4. Piecewise function: $f(x)=1-x^2$ if $x\le 2$, and $f(x)=x$ if $x> 2$

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