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