#include <iostream>
using namespace std;
int main(void){
    // Here your code !
    int n;
    long long cnt=0, a[105][101]={};
    cin >> n;
    a[0][0]=1;
    
    for(int i=0;i<n+1;i++){
        cnt+=a[n][i];
        for(int j=0;j<101;j++){
            a[j+2][i+1]+=a[j][i];
            a[j+1][i+1]+=a[j][i];
        }
    }
    cout<< cnt<<endl;
    return 0;
}