GARD

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

long long nCr(int n, int r) {
    r = min(r, n - r);

    if(r == 0) return 1;

    long long res = 1, k = 1;
    while(r != 0) {
        res *= n; k *= r;

        long long m = __gcd(res, k);
        res /= m; k /= m;

        n--; r--;
    }
    return res;
}

int n, k;
long long dp[55];

long long solve(int p) {
    if(p == 0) return 1;
    if(dp[p] != 0) return dp[p];

    long long sum = 0;
    for(int i = min(p, k); i >= 1; --i)
        sum += nCr(p, i) * solve(p - i);

    return dp[p] = sum;
}

int main()
{
    //freopen("GARD.inp", "r", stdin);
    //freopen("GARD.out", "w", stdout);
    ios_base::sync_with_stdio(false);
    cin.tie(NULL); cout.tie(NULL);

    cin >> n >> k;
    cout << solve(n) << '\n';

    return 0;
}