https://www.acmicpc.net/problem/2747
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Scanner;
public class B2747 {
public static void main(String[] args) throws Exception {
// TODO Auto-generated method stub
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
int num = Integer.parseInt(br.readLine());
int[] fibo = new int[num+1];
fibo[0] = 0;
fibo[1] = 1;
for (int i=2; i<=num; i++) {
fibo[i] = fibo[i-1]+fibo[i-2];
}
System.out.println(fibo[num]);
}
}