public class Euler114 {
    public static void main(String[] args) {
        int len=50; long[] dp=new long[len+1]; dp[0]=1;
        for(int n=1;n<=len;n++){dp[n]=dp[n-1];for(int b=3;b<=n;b++)dp[n]+=(b==n)?1:dp[n-b-1];}
        System.out.println(dp[len]);
    }
}