Description
The numbers of all offices in the new building of the Tax Office of IT City will have lucky numbers.
Lucky number is a number that consists of digits 7 and 8 only. Find the maximum number of offices in the new building of the Tax Office given that a door-plate can hold a number not longer than n digits.
Input
The only line of input contains one integer n (1 ≤ n ≤ 55) — the maximum length of a number that a door-plate can hold.
Output
Output one integer — the maximum number of offices, than can have unique lucky numbers not longer than n digits.
Sample Input
2
6
#include <cstdio>
#include <cstring>
#include <cmath>
#include <cstdlib>
#include <algorithm>
#include <queue>
#include <stack>
#define INF 0x3f3f3f3f
#define eps 1e-8
#define Si(a) scanf("%d", &a)
#define Sl(a) scanf("%lld", &a)
#define Sf(a) scanf("%lf", &a)
#define Ss(a) scanf("%s", a)
#define Pi(a) printf("%d\n", (a))
#define Pf(a) printf("%.2lf\n", (a))
#define Pl(a) printf("%lld\n", (a))
#define Ps(a) printf("%s\n", (a))
#define Wi(a) while((a)--)
#define cle(a, b) memset(a, (b), sizeof(a))
#define MOD 1000000007
#define LL long long
#define PI acos(-1.0)
using namespace std;
int main()
{
int n;
while(Si(n)==1)
{
__int64 ans = 0, num = 1;
for(int i = 1; i <= n; ++i)
{
num<<=1;
ans += num;
}
printf("%I64d\n", ans);
}
return 0;
}