HDU2200

水题～～～

/*
C(N,M)
*/
#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#include<algorithm>
#include<iostream>
#include<queue>
#include<stack>
#include<math.h>
#include<map>
typedef __int64 int64;
using namespace std;
const int maxn = 1005;
int64 solve( int64 n,int64 m ){
    int64 sum=1;
    int64 tt=1;
    for( int64 i=n;i>=n-m+1;i-- ){
        sum=sum*i/tt;
        tt++;
    }
    return sum;
}    
int main(){
    int64 n;
    while( scanf("%I64d",&n)!=EOF ){
        int64 sum=0;
        for( int64 i=2;i<=n;i++ ){
            sum+=( solve( n,i )*( i-1 ) );
        }
        printf("%I64d\n",sum);
    }
    return 0;
}