#include <bits/stdc++.h>

using namespace std;

typedef long long ll;

int main()
{
   int n, k;
   cin >> n >> k;

   vector <vector<ll> > dp(n + 1, vector<ll> (2));

   if (k == 1) {
    cout << 1;
    return 0;
   }


   dp[1][0] = 1;
   dp[1][1] = 1;

   for (int i = 2; i < k; i++) {
        dp[i][0] = dp[i-1][1] + dp[i-1][0];
        dp[i][1] = dp[i-1][1] + dp[i-1][0];
   }

   for (int i = k; i <= n; i++) {
    dp[i][0] = dp[i-1][0] + dp[i-1][1];
    for (int j = i - 1; j > i - k; j--)
        dp[i][1] += dp[j][0];
   }

   cout << dp[n][0] + dp[n][1];

    return 0;
}