已知 $f\left(x\right)=\frac{1}{1+x}$.各项均为正数的数列 $\left\{a_n\right\}$满足 $a_1=1,a_{n+2}=f\left(a_n\right)$.若 $a_{2010}=a_{2012}$，则 $a_{20}+a_{11}$的值是.