백준 2193

import java.util.Scanner;
 
public class Main{
    static public void main(String args[]){
    	Scanner sc = new Scanner(System.in);
    	int n = sc.nextInt();
       
        //f(1)=1, f(2)=1, f(n)=f(n-1)+f(n-2) (n>=2)
    	long dp []=new long [n+1];
        dp[0]=0;
        dp[1]=1;    
        for(int i=2;i<=n;i++){
           dp[i]=dp[i-1]+dp[i-2];
           
        }
      
         
        System.out.println(dp[n]);
	}
     
 }