#include <iostream>

using namespace std;

unsigned long long rs, fib[5000], x;

int main(){

	fib[1] = 1;
	cin >> x;
	while(fib[rs] < x)
	{
	 if(rs > 0)fib[rs + 1] = fib[rs] + fib[rs - 1];
	 rs++;
	}
	if(rs) cout << rs-1;
	else cout << '0';
	
	return (0);
}