#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using vl  = vector<ll>;

#define FOR(i,b,n) for(ll i=(b); i<(n); ++i)

int main() {
	vl step = {1, 2};
	ll n; cin >> n;
	vl dp(n + 1, 0); dp[0] = 1;
	FOR(i, 1, n + 1) for (ll p : step) if (i - p >= 0) dp[i] += dp[i - p];
	cout << dp[n] << endl;

	return 0;
}