#include <bits/stdc++.h>
using namespace std;

int a[1000000];
int n;
long long cnt = 0;
void dfs(int step,int sum)
{
	if(sum > n) return;
    if(sum == n)
    {
        cnt++;
        return;
    }
    a[step] = 1;
    dfs(step+1,sum+1);
    a[step] = 2;
    dfs(step+1,sum+2);
}
int main()
{
    cin >> n;
    dfs(1,0);
    cout << cnt << endl;
    return 0;
}