#include<bits/stdc++.h>
using namespace std;
typedef long long LL;
LL f[55][7];
int main()
{
    int n, m;scanf("%d%d", &n, &m);
    memset(f, 0, sizeof(f));
    f[1][0] = f[1][1] = 1;
    for(int i = 2; i <= n; i++)
    {
        f[i][0] = f[i-1][0];
        for(int j = 1; j <= min(m-1, i); j++)
        {
            f[i][j] = f[i-1][j-1];
            f[i][0] += f[i-1][j];
        }
    }
    LL ans = 0;
    for(int j = 0; j <= m-1; j++) ans += f[n][j];
    printf("%lld\n", ans);
    return 0;
}

#include<bits/stdc++.h>
using namespace std;
typedef long long LL;
LL f[55][7];
int main()
{
    int n,m;scanf("%d%d",&n,&m);
    memset(f,0,sizeof(f));
    f[1][0]=f[1][1]=1;
    for(int i=2;i<=n;i++)
    {
        f[i][0]=f[i-1][0];
        for(int j=1;j<=min(m-1,i);j++)
        {
            f[i][j]=f[i-1][j-1];
            f[i][0]+=f[i-1][j];
        }
    }
    LL ans=0;
    for(int j=0;j<=m-1;j++) ans+=f[n][j];
    printf("%lld\n",ans);
    return 0;
}