[백준] P2193

import java.util.Scanner;

public class P2193 {
	public static void main(String[] args) { // DP 피보나치
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		long dp[] = new long[n + 1]; // 오버플로우 주의
		if(n == 1 || n == 2) {
			System.out.println(1);
			return ;
		}
		
		dp[1] = dp[2] = 1;
		for(int i = 3; i <= n; i++) {
			dp[i] = dp[i-1] + dp[i-2];
		}
		System.out.println(dp[n]);
		
		sc.close();
	}
	
	/* DFS 접근 시간초과
	 
		private static int cnt = 0;
	
		public static void main(String[] args) {
			Scanner sc = new Scanner(System.in);
			int n = sc.nextInt(), dp[] = new int[n];
			dp[0] = 1;
			dfs(dp, 1, 1);
			System.out.println(cnt);
			sc.close();
		}
	
		private static void dfs(int[] dp, int index, int prev) {
			if (index == dp.length) {
				cnt++;
				return;
			}
			if (prev == 1) {
				dp[index] = 0;
				dfs(dp, index + 1, dp[index]);
			} else {
				dp[index] = 0;
				dfs(dp, index + 1, dp[index]);
				dp[index] = 1;
				dfs(dp, index + 1, dp[index]);
			}
		}
		
	*/
}