#include <cstdio>

void suma(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 a[100005], b[100005];

int main(){
	
	freopen("nunta.in","r",stdin);
	freopen("nunta.out","w",stdout);
	
	int n,i;
	
	scanf("%d",&n);
	
	a[0]=1;
	a[1]=0;
	
	b[0]=1;
	b[1]=1;
	
	for(i=1; i<=n; i+=2){
		suma(a,b);
		suma(b,a);
	}
	
	if(n%2==0)
		for(i=a[0]; i>0; i--)
			printf("%d",a[i]);
	else
		for(i=b[0]; i>0; i--)
			printf("%d",b[i]);
		
}