minor add

solutions/gold/usaco-993.mdx

@@ -7,6 +7,7 @@ author: Nathan Gong, Ryan Chou
 
 [Official Analysis (C++)](http://www.usaco.org/current/data/sol_time_gold_jan20.html)
 
+## Explanation
 
 We only need to keep track of the number of days that Bessie has been traveling and the amount of mooney that she has made. For every day up to $T_{\text{max}}$, we'll try to travel to each city, and update the mooney made if the current path is more optimal. The maximum amount of money she makes is $1000t - t^2$, in the case where she makes $1000$ mooney per city and the cost is $1$. Her earnings become negative when $t > 1000$, so we only have to check her movement across the cities for at most $1000$ days.