include <iostream>

include <stdio.h>

include <algorithm>

include <vector>

include <cmath>

include <iomanip>

include <set>

include <map>

include <stack>

include <queue>

include <climits>

define ll long long

define p push_back

define i insert

define rvt reverse(vt.begin(), vt.end())

define svt sort(vp.begin(), vp.end())

define ff first

define ss second

define endl '\n'

define MAX 1e9

using namespace std; int main() { ll n; cin >> n; vector<string> vtf = {"1"},vts = {"1"},vtn; if(n == 1 or n == 2) { cout << "1"; } else { for(ll i = 3; i <= n; i++) { vtn = vtf; while(vtn.size() < vts.size()) { vtn.i(vtn.begin(),"0"); } ll carry = 0; for(ll j = vtn.size() - 1; j >= 0; j--) { ll x = stoll(vtn[j]); ll y = stoll(vts[j]); x = x + y + carry; carry = x/10; vtn[j] = to_string(x%10); } if(carry > 0) { vtn.i(vtn.begin(),to_string(carry%10)); } vtf = vts; vts = vtn; } for(ll i = 0; i < vtn.size(); i++) { cout << vtn[i]; } } } // it is cpp program aimed to find sum of big numbers