#include <bits/stdc++.h>

using i64 = long long;
using u64 = unsigned long long;
using u32 = unsigned;
using u128 = unsigned __int128;
#define lowbit(x) = ((x) & -(x))
#define rep_0(a, b, c) for (int a = b; a < c; a++)
#define rep_1(a, b, c) for (int a = b; a <= c; a++)
#define per(a, b, c) for (int a = b; a >= c; a--)
using namespace std;
string solve_a_add_b(string a, string b)
{
    vector<int> ans;
    stack<int> ans_a;
    stack<int> ans_b;
    for (int i = 0; a[i]; i++)
    {
        ans_a.push(a[i] - 48);
    }
    for (int i = 0; b[i]; i++)
    {
        ans_b.push(b[i] - 48);
    }
    while (!ans_a.empty() && !ans_b.empty())
    {
        int temp_a, temp_b;
        temp_a = ans_a.top();
        ans_a.pop();
        temp_b = ans_b.top();
        ans_b.pop();
        ans.push_back(temp_a + temp_b);
    }
    if (!ans_a.empty())
    {
        while (!ans_a.empty())
        {
            ans.push_back(ans_a.top());
            ans_a.pop();
        }
    }
    else if (!ans_b.empty())
    {
        while (!ans_b.empty())
        {
            ans.push_back(ans_b.top());
            ans_b.pop();
        }
    }
    for (int p = 0; p < ans.size() - 1; p++)
    {

        if (ans[p] >= 10)
        {
            ans[p + 1] += ans[p] / 10;
            ans[p] = ans[p] % 10;
        }
    }
    while (ans.back() >= 10)
    {
        int num = ans.back();
        ans.push_back(num / 10);
        ans[ans.size() - 2] = num % 10;
    }
    string s = "";

    for (int i = ans.size() - 1; i >= 0; i--)
    {
        s += to_string(ans[i]);
    }
    return s;
}
void solve()
{
    int n;
    cin >> n;
    vector<string> a;
    a.push_back("1");
    a.push_back("1");
    a.push_back("2");
    for (int i = 3; i < n; i++)
    {
        a.push_back(solve_a_add_b(a[i - 1], a[i - 2]));
    }
    cout << a[n - 1] << endl;
    return;
}

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int t = 1;
    // cin >> t;

    while (t--)
    {
        solve();
    }

    return 0;
}

package main

import (
	"fmt"
)

func addStrings(a, b string) string {
	i, j := len(a)-1, len(b)-1
	carry := 0
	result := ""

	for i >= 0 || j >= 0 || carry > 0 {
		sum := carry
		if i >= 0 {
			sum += int(a[i] - '0')
			i--
		}
		if j >= 0 {
			sum += int(b[j] - '0')
			j--
		}
		result = string(sum%10+'0') + result
		carry = sum / 10
	}
	return result
}

func main() {
	var n int
	fmt.Scan(&n)
	a := []string{"1", "1", "2"}
	if n <= 3 {
		fmt.Println(a[n])
		return
	}

	for i := 3; i <= n; i++ {
		a = append(a, addStrings(a[i-1], a[i-2]))
	}
	fmt.Println(a[n])
}

n = int(input())
a,b=1,1
for i in range(n):
    a,b=b,a+b
print(a)