#include<iostream> #include<string> #include<iomanip> #include<cmath> #include<vector> #include<algorithm> using namespace std; #define int long long #define rep(i,n) for(int i = 0; i < (n); i++) #define INF ((long long)1e18) #define EPS (1e-5) #define MOD ((int)1e9+7) #define endl "\n" #define yn(f) ((f)?"Yes":"No") #define YN(f) ((f)?"YES":"NO") signed main(){ cin.tie(0); ios::sync_with_stdio(false); cout<<fixed<<setprecision(10); int N; int dp[2][100] = {}; cin>>N; dp[0][0] = 1; for(int i = 0; i < N; i++){ // dp[0][i+1] += dp[1][i]; // dp[0][i+1] += dp[0][i]; // dp[1][i+2] += dp[0][i]; dp[0][i+1] += dp[0][i]; dp[0][i+2] += dp[0][i]; } cout<<dp[0][N]<<endl; return 0; }