Problem 1927. Find nth maximum

Find nth maximum in a vector of integer numbers. Return NaN if no such number exists.

 x = [2 6 4 9 -10 3 1 5 -10];

So

• n_max(x,3) would find 3rd maximum value in x which is 5
• n_max(x,8) would find 8th maximum value in x which is -10
• n_max(x,9) would find 9th maximum value in x which is -10
• n_max(x,12) does not exist so return NaN