#include <iostream>
#include <vector>
#include <set>
#include <map>
#include <queue>
#include <algorithm>
#include <cstring>
#include <cstdio>
#include <fstream>
#include <sstream>
using namespace std;
typedef long long ll;

typedef vector<ll> vec;
typedef vector<vec> matrix;

matrix identity(int n) {
    matrix A(n, vec(n));
    for (int i = 0; i < n; ++i) A[i][i] = 1;
    return A;
}

matrix mul(const matrix &A, const matrix &B) {
    matrix C(A.size(), vec(B[0].size()));
    for (int i = 0; i < C.size(); ++i)
        for (int j = 0; j < C[i].size(); ++j)
            for (int k = 0; k < A[i].size(); ++k)
                C[i][j] += A[i][k] * B[k][j];
    return C;
}

vec mul(const matrix &A, const vec &x) {
    vec y(A.size());
    for (int i = 0; i < A.size(); ++i)
        for (int j = 0; j < A[0].size(); ++j)
            y[i] += A[i][j] * x[j];
    return y;
}

matrix pow(const matrix &A, int e) {
    return e == 0 ? identity((int)A.size())  :
    e % 2 == 0 ? pow(mul(A, A), e/2) : mul(A, pow(A, e-1));
}

int main(){
    int N;
    cin >> N;
    
    matrix A(2, vec(2));
    A[0][0] = 0; A[0][1] = 1;
    A[1][0] = 1; A[1][1] = 1;
    
    vec init(2);
    init[0] = init[1] = 1;
    
    vec res = mul(pow(A, N), init);
    cout << res[0] << endl;
    
    return 0;
}