#include <stdio.h>
#include <string.h>
//斐波那契递归
int f(int n);
int main()
{
    int n;
    while ((scanf("%d", &n)) != EOF)
        printf("%d\n", f(n));

    return 0;
}

int f(int n)
{
    int ret=0;
    if (n == 1)
        ret = 1;
    else if (n == 2)
        ret = 1;
    else if (n == 3)
        ret = 2;
    else{
        ret=f(n-1)+f(n-2);
    }


    return ret;
}