#include<bits/stdc++.h>
using namespace std;
#define ll long long
ll n,c[1000][1000],tong;
void sang()
{
    c[0][0]=1;
    for(ll i=1;i<=100;i++)
    {
        c[i][0]=1;
        c[i][i]=1;
        for(ll j=1;j<i;j++)
            c[i][j]=c[i-1][j-1]+c[i-1][j];
    }
}
int main()
{
    cin>>n;
    ll d1=n;
    ll d2=0;
    sang();
    while(d1>=0)
    {
        tong+=c[d1+d2][d1];
        d1-=2;
        d2++;
    }
    cout<<tong;
}