#include <bits/stdc++.h>
#define REP(i,n) for (int i=0;i<(n);i++)
#define FOR(i,a,b) for (int i=(a);i<(b);i++)
#define dump1d_arr(array,i) cerr << #array << "[" << (i) << "] ==> " << (array[i]) << endl;
#define dump2d_arr(array,i,j) cerr << #array << "[" << (i) << "]" << "[" << (j) << "] ==> " << (array[i][j]) << endl;
#define dump(x)  cerr << #x << " => " << (x) << endl;
#define CLR(vec) { REP(i,vec.size()) vec[i] = 0; } 
#define MIN(a, b) ((a) < (b) ? (a) : (b))
#define MAX(a, b) ((a) > (b) ? (a) : (b))

using namespace std;

typedef long long LL;
typedef vector<LL> VLL;

int main(void){
	short N;
	cin >> N;

	VLL dp(N+1,0);
	dp[0] = 1;
	dp[1] = 1;

	FOR(i,2,N+1){
		dp[i] = dp[i-1] + dp[i-2];
	}

	cout << dp[N] << endl;

	return 0;
}