#include<stdio.h>
int main()
{
    int n,i;
    int f[14];
    printf("Input n(13>=n>=2):");
    scanf("&d",&n);
    for(i=0;i<=n;i++)
    {
        if(i==0)
        {
            f[i]=0;
        }
        else if(i==1)
        {
            f[i]=1;
        }
        else if(i==2)
        {
            f[i]=2;
        }
        else
        {
            f[i]=2*f[i-1]+f[i-2]*f[i-3];
        }
    }
    printf("\nf(%d)=%d",i,f[i]);
    return 0;
}