#include <bits/stdc++.h>
#define FI(_n) for(int i = 0;i<(_n);i++)
#define FJ(_n) for(int j = 0;j<(_n);j++)
#define pb push_back
#define all(c) c.begin(),c.end()
using namespace std;
typedef long long ll;
const ll INF = 1e18 + 1;
#define ndbg 1
int main()
{
    ios_base::sync_with_stdio(0);
#ifdef ndbg
  ifstream cin("input.txt");
  ofstream cout("output.txt");
#endif
    cin.tie(0);cout.tie(0);

    ll n, k;
    cin >> n >> k;
    if(k == 0)
    {
        cout << ((n + 1) % 10 == 0 ? ( (n + 1) % 100 / 10 == 0 ? (n + 1) % 1000 / 100 : (n + 1) % 100 / 10) : (n + 1) % 10 );
        return 0;
    }
    ll fact[] = {1, 1, 2, 6, 24};
    ll sum = 0;
    for(int i = 0; i <= min(1ll*4, n); i++)
    {
        ll ch = 1;
        for(int j = 0; j < k; j++) ch *= fact[i];
        sum += ch;
    }
    while(sum % 10 == 0) sum /= 10;
    cout << sum % 10;



#ifdef ndbg
  cin.close();
  cout.close();
#endif
    return 0;
}