import java.util.Scanner;
 
public class Main {
	public static void main (String[] args) {
		// считывание переменной n
		Scanner scanner = new Scanner(System.in);
		int n = scanner.nextInt();
 
		// получение n-ого по счёту числа Фибоначчи
		long a = 0;
		long b = 1;
		for (int i = 2; i <= n; ++i) {
			long next = a + b;
			a = b;
			b = next;
		}
 
		// вывод n-ого по счёту числа Фибоначчи
		System.out.println(b);
	}
}

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NDY=

46