#include <iostream>
#include <fstream>
using namespace std;

ifstream fin ("nunta.in");
ofstream fout ("nunta.out");

const int maxn = 1005;
int n, V[2][maxn];

void Add(int A[], int B[]) {
    int i, t = 0;
    for (i = 1; i <= A[0] || i <= B[0] || t; i++) {
        t += A[i] + B[i];
        A[i] = t % 10;
        t /= 10;
    }
    A[0] = i - 1;
}

int main() {
    ios_base :: sync_with_stdio(false);
    int i;
    fin >> n;
    V[0][0] = V[0][1] = V[1][0] = V[1][1] = 1;
    for (i = 2; i <= n; i++) {
        Add(V[i & 1], V[!(i & 1)]);
    }
    for (i = V[n & 1][0]; i > 0; i--) {
        fout << V[n & 1][i];
    }
    fin.close();
    fout.close();
    return 0;
}