3. Given the function
$$
f(x)=x^{2}-53 x+196+\left|x^{2}-53 x+196\right| \text {. }
$$

Then $f(1)+f(2)+\cdots+f(50)=(\quad)$.
(A) 660
(B) 664
(C) 668
(D) 672
3. A.

Notice that, $x^{2}-53 x+196=(x-4)(x-49)$. When $4 \leqslant x \leqslant 49$,
$$
x^{2}-53 x+196 \leqslant 0, f(x)=0 \text {. }
$$

When $x<4$ or $x>49$,
$$
\begin{array}{l}
f(x)=2(x-4)(x-49) . \\
\text { Hence } f(1)+f(2)+\cdots+f(50) \\
=f(1)+f(2)+f(3)+f(50) \\
=2(3 \times 48+2 \times 47+1 \times 46+46 \times 1)=660 .
\end{array}
$$