#include <bits/stdc++.h>

using namespace std;

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

typedef int nr[215];
nr a, b, *f = &a, *s = &b;
void add(nr *ptr_a, nr *ptr_b) {
    int t = 0;
    if ((*ptr_a)[0] < (*ptr_b)[0])
        (*ptr_a)[0] = (*ptr_b)[0];
    for (int i = 1; i <= (*ptr_a)[0]; i++) {
        t += (*ptr_a)[i] + (*ptr_b)[i];
        (*ptr_a)[i] = t % 10;
        t /= 10;
    }
    while (t)
        (*ptr_a)[++(*ptr_a)[0]] = t % 10, t /= 10;
}

int main() {
    int n;
    fin >> n;
    b[0] = b[1] = 1;
    for (int i = 1; i <= n; i++) {
        add(f, s);
        swap(f, s);
    }

    for (int i = (*s)[0]; i >= 1; i--)
        fout << (*s)[i];
    return 0;
}