#include <iostream>
#include <fstream>
#include <vector>

using namespace std;

ifstream fin("kfib.in");
ofstream fout("kfib.out");
int n;
vector<int> mem;

int fib(int k)
{
    int rez = 0;
    if (mem[k] != 0)
        return mem[k];
    if (k <= 2)
    {
        rez = 1;
    }
    else
    {
        rez = fib(k - 1) + fib(k - 2);
    }
    mem[k] = rez;
    return rez;
}

int main()
{
    fin >> n;
    mem.resize(n + 1);
    fout << fib(n);
    return 0;
}