#include <iostream>
#include <fstream>
using namespace std;

const int MAXN=210;
//int v[MAXN];

ifstream f("nunta.in");
ofstream g("nunta.out");

int N;
unsigned char F1[MAXN]={1,1},F2[MAXN]={1,2};

unsigned char *s1=F1,*s2=F2,*sx;

void afis(unsigned char A[])
{
    for(int i=A[0];i>=1;i--)
        g<<(int)A[i];
}

int adunare(unsigned char A[], unsigned char B[])
{
    ///calculam A<--A+B
    int T = 0;
    if(A[0]<B[0])A[0]=B[0];
    for(int i = 1; i <= A[0]; i++)
    {
        T += A[i]+ B[i];
        A[i] = T % 10;
        T /= 10;
    }
    if(T>0)
        A[++A[0]]=1;
}

int main()
{
    f>>N;
    if(N<=2)s2[1]=N;
    else
        for(int i=3;i<=N;i++)
        {
        adunare(s1,s2);
        sx=s1;
        s1=s2;
        s2=sx;
        }
    afis(s2);
    return 0;
}