#include <cstdio>
#include <algorithm>

using namespace std;

unsigned long long fib[512];

int main ()
{
    fib[0] = 0LL;
    fib[1] = 1LL;

    unsigned long long x;
    scanf ("%llu", &x);

    int i = 1;
    for (; fib[i] < x; ++i)
        fib[i + 1] = fib[i] + fib[i - 1];

    printf ("%d\n", i - 1);

    return 0;
}