Question 79
Let $a_1, a_2, \dots, a_n$ be $n$ non-negative real numbers.
$$
\frac{1}{1+a_1} + \frac{a_1}{(1+a_1)(1+a_2)} + \dots + \frac{a_1a_2\dots a_{n-1}}{(1+a_1)(1+a_2)\dots(1+a_n)} \le 1.
$$
$$
\frac{1}{1+a_1} + \frac{a_1}{(1+a_1)(1+a_2)} + \dots + \frac{a_1a_2\dots a_{n-1}}{(1+a_1)(1+a_2)\dots(1+a_n)} \le 1.
$$