import java.io.*;
import java.util.*;
public class Main{
public static void main(String[] args) throws Exception{
Scanner sc = new Scanner(System.in);
while(sc.hasNextInt()){
int month = sc.nextInt();
System.out.println(fun(month));
}
}
public static int fun(int month){
if (month <= 2) return 1;
int[] array = new int[month + 1];
array[1] = array[2] = 1;
for (int i = 3; i <= month; i++) {
array[i] = array[i - 1] + array[i - 2];
}
return array[month];
}
}
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