include[HTML_REMOVED]

include[HTML_REMOVED]

include[HTML_REMOVED]

using namespace std;
int n;
int cmt=0;
void f(int k){
if(k==n) cmt++;
else if(k<n){
f(k+1);
f(k+2);
}
}
int main(){

cin>>n;
f(0);
cout<<cmt<<endl;
return 0;

}