# include<bits/stdc++.h>
using namespace std;
string add(string a , string c) {
	long long int l[10000], k[10000], h[10000], j;
	string g;
	g = "";
	for (int q = 0 ; q < a.size() ; q++) {
		l[q] = a[a.size() - q - 1] - '0';
	}
	for (int q = 0 ; q < c.size() ; q++) {
		k[q] = c[c.size() - q - 1] - '0';
	}
	j = max (a.size() , c.size());
	for (int q = 0 ; q < j ; q++) {
		h[q] = k[q] + l[q];
	}
	for (int q = 0 ; q < j ; q++) {
		h[q + 1] += h[q] / 10;
		h[q] %= 10;
	}
	if (h[j]) {
		j++;
	}
	for (int q = j - 1 ; q >= 0 ; q--) {
		g += (char)(h[q] + '0');
	}
	return g;
}
int main() {
	int n;
 	cin >> n;
	string m[n], b, v;
	m[0] = "1";
	m[1] = "1";
	b = "1";
 	for (int q = 0 ; q < n - 1 ; q++) {
 		v = m[q];
 		b = add(v , m[q + 1]);
 		m[q + 2] = b;
	}
	cout << b;
    return 0;
}