C :

#include <stdio.h>
long long fun(int x)
{
	if(x==1)
	return 0;
	if(x==2)
	return 1;
	else
	return ((x-1)*(fun(x-2)+fun(x-1)));
}
int main()
{
	int n;
	while(scanf("%d",&n)!=EOF)
	{
		printf("%lld\n",fun(n));
	}
	return 0;
}

C++ :

#include <bits/stdc++.h>
using namespace std;
#define maxn 100000007
int main()
{
	int d[1005];
	d[2]=1;d[1]=0;
	for (int i=3;i<999;i++){
		d[i]=(i-1)*(d[i-1]+d[i-2])%maxn;
	}
	
	int n;
	while(~scanf("%d",&n)){
		printf("%d\n",d[n]);
	}
	
	return 0;
}