#include <bits/stdc++.h>
using namespace std;
template <typename T, typename T1>
ostream &operator<<(ostream &out, pair<T, T1> obj) {
  out << "(" << obj.first << ", " << obj.second << ")";
  return out;
}
template <typename T, typename T1>
ostream &operator<<(ostream &out, map<T, T1> cont) {
  typename map<T, T1>::const_iterator itr = cont.begin();
  typename map<T, T1>::const_iterator ends = cont.end();
  for (; itr != ends; ++itr) out << *itr << " ";
  out << endl;
  return out;
}
template <typename T>
ostream &operator<<(ostream &out, set<T> cont) {
  typename set<T>::const_iterator itr = cont.begin();
  typename set<T>::const_iterator ends = cont.end();
  for (; itr != ends; ++itr) out << *itr << " ";
  out << endl;
  return out;
}
template <typename T>
ostream &operator<<(ostream &out, multiset<T> cont) {
  typename multiset<T>::const_iterator itr = cont.begin();
  typename multiset<T>::const_iterator ends = cont.end();
  for (; itr != ends; ++itr) out << *itr << " ";
  out << endl;
  return out;
}
template <typename T,
          template <typename ELEM, typename ALLOC = allocator<ELEM>> class CONT>
ostream &operator<<(ostream &out, CONT<T> cont) {
  typename CONT<T>::const_iterator itr = cont.begin();
  typename CONT<T>::const_iterator ends = cont.end();
  for (; itr != ends; ++itr) out << *itr << " ";
  out << endl;
  return out;
}
template <typename T, unsigned int N, typename CTy, typename CTr>
typename enable_if<!is_same<T, char>::value, basic_ostream<CTy, CTr> &>::type
operator<<(basic_ostream<CTy, CTr> &out, const T (&arr)[N]) {
  for (auto i = 0; i < N; ++i) out << arr[i] << " ";
  out << endl;
  return out;
}
template <typename T>
T gcd(T a, T b) {
  T min_v = min(a, b);
  T max_v = max(a, b);
  while (min_v) {
    T temp = max_v % min_v;
    max_v = min_v;
    min_v = temp;
  }
  return max_v;
}
template <typename T>
T lcm(T a, T b) {
  return (a * b) / gcd(a, b);
}
template <typename T>
T fast_exp_pow(T base, T exp, T mod) {
  T res = 1;
  while (exp) {
    if (exp & 1) {
      res *= base;
      res %= mod;
    }
    exp >>= 1;
    base *= base;
    base %= mod;
  }
  return res % mod;
}
int N, K;
int noMatch[10];
long long answer = 1;
long long coeff(int val1, int val2) {
  long long ret = 1;
  val2 = min(val2, N - val2);
  for (auto i = 1; i <= val2; ++i) {
    ret *= val1;
    --val1;
  }
  for (auto i = 1; i <= val2; ++i) {
    ret /= i;
  }
  return ret;
}
int main() {
  scanf("%d%d", &N, &K);
  for (auto i = 1; i <= K; ++i) {
    vector<int> perm;
    for (auto j = 1; j <= i; ++j) {
      perm.push_back(j);
    }
    do {
      int diff = 0;
      for (auto j = 0; j < perm.size(); ++j) {
        if (j + 1 != perm[j]) {
          ++diff;
        }
      }
      if (diff == perm.size()) {
        ++noMatch[i];
      }
    } while (next_permutation(perm.begin(), perm.end()));
  }
  for (auto i = N - K; i <= N; ++i) {
    answer += coeff(N, i) * noMatch[N - i];
  }
  printf("%lld\n", answer);
  return 0;
}
