#include <stdio.h>
int F(int n)
{
        if(n==1||n==2)
            return 1;
        else
            return F(n-1)+F(n-2);
}
int main() {
    int n=0;
    scanf("%d",&n);
    //1 2 3 4 5 6 7 8
    //1 1 2 3 5
    int sum=F(n);
    printf("%d",sum);
    return 0;
}