import java.util.*;
public class Main{
    public static void main(String[]args){
        Scanner diva = new Scanner(System.in);
        int n = diva.nextInt();
        
        if(n<=0){
            System.out.print("Invalid input");
        }
      
        int a = 0;
        int b = 1;
        while(a<n){
            int c = a+b;
                a = b;
                b = c;
                c++;
        }
        System.out.print(c);
    }
}