#include <stdio.h>
int Fib(int n)
{
    if (n == 1)
        return 1;
    else if (n == 2)
        return 2;
    else
        return Fib(n-1) + Fib(n-2);
}
int main()
{
    int n = 0;
    scanf("%d",&n);
    int ret = Fib(n);
    printf("%d",ret);
    return 0;
}