#include <stdio.h>

int main()
{
    int x;
    extern int fib(int x);
    while (scanf("%d", &x) == 1)
        printf("%d\n", fib(x));
    return 0;
}


int fib(int x)
{
    if (x < 3)
        return 1;
    else
        return fib(x-1) + fib(x-2);
}