#include <iostream>
#define DM 1000000
using namespace std;

long long a, s[DM];
int i;

int main ()
{
    s[0] = 0;
    s[1] = 1;
    cin >> a;
    if (a == 1)
    {
        cout << 0;
        return 0;
    }
    if (a == 2)
    {
        cout << 1;
        return 0;
    }
    if (a == 3)
    {
        cout << 2;
        return 0;
    }
    for (i = 2; s[i-1] < a; ++i)
        s[i] = s[i-1] + s[i-2];
    cout << i-2;
    return 0;
}