E - Group work

教育研究表明小组学习有诸多益处,老师想知道班级N名学生能组成多少不同小组,要求每组至少2人,两组至少有一名学生不同则为不同组。需根据给定N值计算可分组数量,给出了输入输出示例及约束条件。

Recent studies in Education show great pedagogical benefits of working in groups, especially in the freshman and sophomore years in high school. Different groups of various sizes are great and allow students to understand their differences and to train in teamwork. A teacher at a modern school wants to know how many different groups he can form in this class of NN students. The only requirement is that a group must have at least 2 students, and two groups are distinct if at least one student is in one of them and no in the other.

Your task in this problem is, given NN, compute the number of distinct groups that is possible to create in the class.

Input

A single line with an integer NN.

Constraints

  • 1≤N≤301≤N≤30

Output

A single line with the number of distinct groups that is possible to have in the class.

Examples

Input

2

Output

1

Input

3

Output

4

Note

In the first example we have two students, therefore we can only have one group. In the second example we have three students, say AA, BB and CC. We can form the groups ABAB, ACAC, BCBC and ABCABC.

#include <iostream>
#include<cstdio>
#include<algorithm>
#include<cstring>
using namespace std;
typedef long long ll;
int main()
{
    int n;
    while(scanf("%d",&n)!=EOF)
    {
        ll ans=1;
        for(int i=1;i<=n;i++)
        {
            ans*=2;
        }
     ans-=(ll)(n+1);
     printf("%lld\n",ans);
    }
    return 0;
}

 

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