#include <iostream>
using namespace std;
int N;
int current=1;
int D[22];
int main() {
cin >> N;
D[4]=1;
for(int x=2; x<=N; x++) {
if(x%2==0) {
D[x+4] += current;
}
else {
D[x+3] +=current;
}
current *= 2;
current -= D[x];
}
cout << current;
}