Codeforces--630F--Selection of Personnel（组合数）


[align=center]F -Selection of Personnel[/align]
Crawling in process...Crawling failedTime
Limit:500MS Memory Limit:65536KB
64bit IO Format:%I64d & %I64u

SubmitStatus

Description

One company of IT City decided to create a group of innovative developments consisting from5 to
7 people and hire new employees for it. After placing an advertisment the company receivedn resumes. Now the HR department has to evaluate each possible group composition and select one of
them. Your task is to count the number of variants of group composition to evaluate.

Input

The only line of the input contains one integer n (7 ≤ n ≤ 777) — the number of potential employees that sent resumes.

Output

Output one integer — the number of different variants of group composition.

Sample Input

Input

7

Output

29

给n个人，然后判断从中取出5,6，7个人的情况有多少，C(n,5)+C(n,6)+C(n,7)

#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
using namespace std;
__int64 C(__int64 n,__int64 m)
{
int num=1;
__int64 ans=1;
while(m--)
{
ans*=(n-m);
ans/=num;
num++;
}
return ans;
}
int main()
{
__int64 n;
while(cin>>n)
{
__int64 ans=0;
for(__int64 i=5;i<=7;i++)
ans+=C(n,i);
cout<<ans<<endl;
}
}

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