1. Let the function $f(x)$ have a domain and range both equal to $R$, and for any $a, b \in R$ there is $f[a f(b)]=a b$. Then the value of $|f(1995)|$ is $\qquad$
Ni, i. 1995.
For the known functional equation, substituting $a=1, a=b, a=f(b)$, we have $f(f(b))=b, f(b f(b))=b^{2}, f\left[f^{2}(b)\right]=b f(b)$. Applying the function $f$ to the third equation, $f\left\{f\left[f^{2}(b)\right]\right\}=f(b f(b))=b^{2}$. Thus, from $f(J(b))=b$, we have $f^{2}(b)=b^{2}$, i.e., $|f(b)|=b$. Therefore, $|f(1995)|=1995$.