/* package whatever; // don't place package name! */
 
import java.util.*;
import java.lang.*;
import java.io.*;
 
/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
	public static int pows(int n){
		if(n == 1 || n==2){
			return 1;
		}
		return (pows(n - 1) + pows(n - 2));
	}
	public static void main (String[] args) 
	{
		int n, i = 0;
		Scanner S = new Scanner (System.in);
		n = S.nextInt();
		System.out.print(pows(n));
 
	}
}

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