#include<stdio.h>
#include<math.h>

int calcola_fib(int N,float *o);

int main()
{
    int n_fib;
    int N;
    float *o;
    int prec=0;
    int corr=1;
    (*o)=((1+(sqrt(5)))/(sqrt(5)));
    scanf("%d",&N);
    while(corr!=N)
    {
        corr=corr+prec;
        prec=corr;
    }
    n_fib=calcola_fib(N,o);
    if(prec==n_fib)
    printf("%d\n",n_fib);
    return 0;
}

int calcola_fib(int N,float *o)
{
    int n_fib;
    int x=0;
    while(x!=N)
    {
        (*o)=(*o)*(*o);
    }
    n_fib=(((*o)+(1/(*o)))/2);
    return(n_fib);
}