import java.io.*;

class Main{
public static void main(String[] args) throws IOException{
BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
String line="";
long[] dp;
while((line=br.readLine())!=null){
int n=Integer.parseInt(line);
dp=new long[n+1];
dp[0]=1;
dp[1]=1;
for(int i=2;i<=n;i++){
dp[i]=dp[i-1]+dp[i-2];
}
System.out.println(dp[n]);
}
}
}