#include<iostream>
#include<math.h>
using namespace std;
double dem_xau(int n, int k)
{
if (n < k) return pow(2, n);
else if (n == k) return pow(2, n) - 1;
else return (dem_xau(n - k, k) + dem_xau(n - 1, k));
}
int main()
{
int n, k;
cout << "dem so xau nhi phan do dai n(n>=1) khong chua k(k>=2) so 0 lien tiep"<< endl;
cout << "n=";
cin >> n;
cout << endl;
cout << "k=";
cin >> k;
dem_xau(n, k);
getchar();
return 0;
}