[alg.search] fixed search_n's Returns part

Author: andreyfe1

source/algorithms.tex

@@ -3998,7 +3998,8 @@
 such that for every non-negative integer \tcode{n} less than \tcode{count}
 the following corresponding conditions hold:
 \tcode{*(i + n) == value, pred(*(i + n),value) != false}.
-Returns \tcode{last} if no such iterator is found.
+Returns \tcode{first} if \tcode{count <= 0},
+otherwise returns \tcode{last} if no such iterator is found.
 
 \pnum
 \complexity