2018

#include <stdio.h>
/// n = new o = old
/// n(i) = o(i-1)
/// o(i) = o(i-1) + n(i-3)
/// sum(i) = o(i) + n(i) + mid
/// so: i miss the mid
/// ex:fib
int f(int i)
{
    int a[55] = {0,1,2,3,4};
    if(i<4)
        return a[i];
    else
        return f(i-1) + f(i-3);
}
int main(void)
{
    int n;
    while(scanf("%d",&n))
    {
        printf("%d\n",f(n));
    }
    return 0;
}

#include <ctype.h>
#include <stdio.h>

int main(void)
{
    int n, i;
    int fab[55] = {1, 2, 3, 4, 6};

    for (i = 5 ; i < 55 ; i++)
        fab[i] = fab[i - 1] + fab[i - 3];

    while (scanf("%d", &n), n)
    {
        printf("%d\n", fab[n - 1]);
    }

    return 0;
}