Answer
procedure smaller $( a_1, a_2, a_3, ... a_n: $ a sequence of positive integers$)$
for $i:=2$ to $n$
$\space\space\space$ if $a_i \lt a_{i-1}$ then return $a_i$
return $-1$
{Note that since it is a set of positive integers, returning $-1$ in this case does indicate a null result}
Work Step by Step
This algorithm attempts to find the first term in a sequence that is less than the preceding term. It does this by comparing each term to the one before it.
Note also the comment attached under the null value $-1$.
