Exciting offer….!!!   It’s World Cup time…. :)  Here is an offer awaiting for you i.e… you will get a ticket to watch world cup finals @ Australia. Your task is so simple. You will be given a function . In order to win the prize, you need to reduce the time complexity of that function.

fun( n)  
{ 
       if (n==0)  
                return 1;  
        if (n==1)  
                 return 2;  
        return fun(n-1) + fun(n-1);  
}

Come on….!!! Hurry up. Solve it and get your ticket for #WC_Finals.


Input
Single integer is given as input which is n value to be used as an argument for the function. 

Output
Return the output generated by the function for given n 
 

Constraints

1 ≤ n ≤ 100

Example
Input:
2

Output:
4
n=int(input())
def fun( n):
	if n==0:
		return 1
	if n==1:
		return 2
	return 2*fun(n-1)
ans=fun(n)	
print ans