#include <fstream>
#include <iostream>

using namespace std;

int a[103],b[103],n;

void Aduna(int A[],int B[])
{
    int t=0,i;
    for(i=1;i<=A[0] || i<=B[0] || t;i++,t/=10)
        A[i]=(t+=(A[i]+B[i]))%10;
    A[0]=i-1;
}

int main()
{
    int i,x,ind;
    ifstream fin("nunta.in");
    fin>>n;
    fin.close();
    a[0]=a[1]=1;
    b[0]=b[1]=1;
    for(i=3;i<=n+1;++i)
        if(i%2==0)
            Aduna(a,b);
        else
            Aduna(b,a);
    ofstream fout("nunta.out");
    if(n%2==1)
        for(i=a[0];i>=1;--i)
            fout<<a[i];
    else
        for(i=b[0];i>=1;--i)
            fout<<b[i];
    fout<<"\n";
    fout.close();
    return 0;
}