After dealing with his 
~n~ rocks for too long, Bob decides to pawn some of them off: he will pawn off the most valuable group of rocks, valued by their age in years. In accordance with the buyers, Bob can only sell rocks of the same age.
Since Bob is busy dealing with the buyers, he wants you to tell him which age of rocks to sell!
Input Specification
The first line of input will contain ~n~ 
~(1 \le n \le 1\,000\,000)~, the total number of rocks.
The second line will contain ~n~ integers 
~(0 \le A_i \le 50)~, representing the age, in years, of each rock.
Output Specification
The age of the rocks Bob should sell to maximize his revenue.
Note: It is guaranteed that there is only 
~1~ maximal answer.
Sample Input 1
10
1 5 9 0 3 10 3 9 3 2
Sample Output 1
9
Explanation for Sample Output 1
Bob has rocks of 
~7~ distinct ages: 
~0, 1, 2, 3, 5, 9, 10~. Out of these ages, he can sell 
~2~ rocks of age 
~9~ for a total of 
~18~ dollars 
~(2 \times 9 = 18)~; the second-best age would be 
~10~ for a total of ~10~ dollars 
~(1 \times 10 = 10)~.
Comments
Neat little problem for intro to time complexity.
I gotta find a way to use this somewhere. Thank you!