#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;

int n,i,a[500],b[500],c[500],*A,*B,*C;

void add(int *A,int *B) {
     int i,t=0;
     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()
{
  freopen("nunta.in","r",stdin);
  freopen("nunta.out","w",stdout);

  scanf("%d",&n); A=a; B=b; C=c;
  A[0]=A[1]=B[0]=C[0]=C[1]=1; B[1]=2;

  for(i=3;i<=n;++i) add(A,B),swap(A,B);

  for(i=B[0];i>=1;--i) printf("%d",B[i]);

 return 0;
}