解法：

暴力

#include <iostream>
#include <vector>
using namespace std;
#define endl '\n'

int main() {
	ios::sync_with_stdio(false);
	cin.tie(0); cout.tie(0);
	int n;
	long long sum = 0, a;
	cin >> n;
	for (int i = 1; i <= n; i++) {
		a = 1;
		for (int j = 1; j <= i; j++) {
			a *= 2;
		}
		sum += a;
	}
	cout << sum << endl;
	return 0;
}