#include <bits/stdc++.h>
using namespace std;

#define LL long long

LL countDer(int n)
{
	// Create an array to store
	// counts for subproblems
	LL der[n + 1];

	// Base cases
	der[0] = 1LL ;
	der[1] = 0LL ;
	der[2] = 1LL ;

	// Fill der[0..n] in bottom up manner
	// using above recursive formula

	for (int i = 3; i <= n; ++i)
		der[i] = (i - 1) * (der[i - 1] + der[i - 2]);


	// Return result for n
	return der[n];
}

// Driver code
int main()
{
	int n = 100 ;
	cout << "Count of Derangements is "
		<< countDer(n);
	return 0;
}