import java.util.*;
import java.math.*;

public class Main {
    static final int maxn = 200 + 5;
    
    public static void main(String[] args) {
        BigInteger[][] f = new BigInteger[maxn][2];
        f[0][0] = BigInteger.ZERO;
        f[0][1] = BigInteger.ONE;
        for(int i = 1; i < maxn; ++i) {
            f[i][0] = f[i - 1][0].add(f[i - 1][1]);
            f[i][1] = f[i - 1][0];
        }
        Scanner cin = new Scanner(System.in);
        while(cin.hasNext()) {
            int n = cin.nextInt();
            System.out.println(f[n][0].add(f[n][1]));
        }
        cin.close();
    }
}