#include <iostream>
#include <fstream>

using namespace std;

ifstream fin("kfib.in");
ofstream fout("kfib.out");

long long A[100000001];
long long N;

int Fibo(long long N)
{
    if(N == 1 || N == 2) return 1;
    A[1] = 1;
    A[2] = 1;
    for(int i = 3 ; i <= N ; ++i)
    {
        A[i] = A[i - 1] + A[i - 2];
    }
    return A[N];

}

int main()
{
    fin >> N;
    fout << Fibo(N);
    return 0;
}