An bydrocarbon is an organic compound which contains only carbons and hydrogens. An isomer is a compound that has the same number of carbons but different structures. Heptane, for example, is a hydrocarbon with 7 carbons. It has nine isomers. The structural formula of three are shown in Figure 1. Carbons are represented by the letter C, and bonds between carbons are represented by a straight line. In all figures, hydrogens are not represented for simplicity. Each carbon can be connected to a maximum of 4 carbons.

<image>
---
Figure 1: These three examples of isomers of heptane have the same number of carbons but different structures.
---



Let define a chain in an isomer as a sequence of connected carbons without branches. An isomer can have many chains of the same length. Figure 2 shows the longest chain of carbons for each of the represented isomer. Note that there can be many instances of longest chain in an isomer.

<image>
---
Figure 2: The figures shows one instance of longest chain of carbons in each isomer. The first and the second isomers show longest chains of 5 carbons. The longest chain in the third isomer has 4 carbons.
---



Your task is to identify the number of carbons of the largest possible carbon compound whose longest carbon chain has n (1 ≤ n ≤ 30) carbons.



Input

Each input contains a list of number of carbons, i.e. the length of a carbon chain.

The number of input lines is less than or equal to 30.

Output

For each number n in input, identify the number of carbons of the largest possible carbon compound whose longest carbon chain has n carbons.

Example

Input

1
4


Output

1
8
#include <iostream>
using namespace std;
int n, f[33];
int main() {
	f[1] = 1, f[2] = 2, f[3] = 5;
	for (int i = 4; i <= 30; i++) {
		if (i & 1) {
			f[i] = 4;
			for (int j = 1; j < i / 2; j++) f[i] *= 3;
			f[i] += f[i - 2];
		}
		else {
			f[i] = 1;
			for(int j = 1; j < i / 2; j++) f[i] *= 3;
			f[i] += f[i - 1];
		}
	}
	while (cin >> n) {
		cout << f[n] << endl;
	}
	return 0;
}