import java.io.OutputStream; import java.io.IOException; import java.io.InputStream; import java.io.PrintWriter; import java.util.Scanner; /** * Built using CHelper plug-in * Actual solution is at the top */ public class Main { public static void main(String[] args) { InputStream inputStream = System.in; OutputStream outputStream = System.out; Scanner in = new Scanner(inputStream); PrintWriter out = new PrintWriter(outputStream); Task solver = new Task(); solver.solve(1, in, out); out.close(); } static class Task { public void solve(int testNumber, Scanner in, PrintWriter out) { final int n = Integer.parseInt(in.next()); long[] dp = new long[n]; dp[n - 1] = 1; dp[n - 2] = 2; for (int i = n - 3; i >= 0; i--) dp[i] = dp[i + 1] + dp[i + 2]; out.println(dp[0]); } } }