#include <bits/stdc++.h>

using namespace std;

#define vi vector<int>
#define ll long long
#define pb push_back
#define mp make_pair
#define ii pair<int,int>

int mod = 10;

long long arranjo(long long n, long long k){
	long long arranjo = 1;

	for (int i = n; i > n-k; --i)
	{
		arranjo = arranjo * i;
	}

	while((arranjo%10)==0)
	{
		arranjo/=10;
	}

	return arranjo%10;
}

int main(){

	long long n,m;

	cin >> n;
	cin >> m;

	cout << arranjo(n,m) << endl;

  return 0;
}


/*
compilar
g++ arquivo.cpp -std=c++11 -o executavel
*/