#include <iostream>
using namespace std;
 int main()
{
   long  a,b,x;
int n;
   cin>>x
   a = 0;
 b = 1;
n=0;
while(a < x - b) {
    long long c = a + b;
    a = b;
    b = c;
    ++n;
}
cout<<n;
return 0;
}