public class Euler117 {
    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];if(n>=2)dp[n]+=dp[n-2];if(n>=3)dp[n]+=dp[n-3];if(n>=4)dp[n]+=dp[n-4];}
        System.out.println(dp[len]);
    }
}