#include <iostream>
using namespace std;
long long a[100],n;
int main() {
	cin >> n;
	a[1]=2;
	a[2]=3;
	for(int i=3;i<=100;i++){
		a[i]=a[i-1]+a[i-2];
	}
	int i=1;
	while(a[i+1]<=n) i++;
	cout<<i;
	return 0;
}