#include<iostream>
#include<string>
#include<cstring>
#include<cstdio>
#include<cmath>
#include<cstdlib>
#include<vector>
#include<set>
#include<map>
#include<queue>
#include<functional>
#include<algorithm>
#define ms0(a) memset(a,0,sizeof(a))
#define ms1(a) memset(a,-1,sizeof(a))
#define pb(a) push_back(a)
using namespace std;
//typedef __int64 ll;
const double Eps = (double)0.5;
const int M = 1e9 + 7;
const int N = 205;
const int L = 55;
const double PI = acos(-1.0);
//int t1[10],t2[10]
int dp[N][2][L + 5];
int main()
{
    int n;
    while(cin>>n)
    {
       // cin>>n;
        memset(dp,0,sizeof(dp));
        dp[0][0][0] = 0;
        dp[0][1][0] = 1;
        for(int i=1; i<= n; i++)
        {
            int pr = 0;
            for(int j = 0; j < L; j++)
            {
                dp[i][0][j] = (dp[i-1][0][j] + dp[i-1][1][j] + pr);
                if(dp[i][0][j] > 9)
                {
                    pr = dp[i][0][j]/10;
                    dp[i][0][j] %= 10;
                }
                else
                    pr = 0;
            }
            for(int j = 0; j<L; j++)
            {
                dp[i][1][j] = dp[i-1][0][j];
            }
            //dp[i][0] = dp[i-1][0] + dp[i-1][1];
            //dp[i][1] = dp[i-1][0];
        }
        int pr = 0;
          for(int j = 0; j < L; j++)
            {
                 dp[n][0][j] = (dp[n][0][j] + dp[n][1][j] + pr);
                 if (dp[n][0][j] > 9)
                 {
                     pr =  dp[n][0][j] / 10;
                     dp[n][0][j] %= 10;
                 }
                 else
                    pr = 0;
            }
            int k;
            for(k = L; k >= 0; k--)
            {
                if(dp[n][0][k])
                    break;
            }
            for(int i= k; i>=0; i--)
                cout<<dp[n][0][i];
            cout<<endl;
        //printf("%I64d\n", dp[n][0] + dp[n][1]);
    }
}