#include <stdio.h>

int main()
{
    int X;
    scanf ("%d", &X);

    if (X==1) {
        printf ("%d\n", 1);
        return 0;
    }

    int N;
    unsigned long long a, b, c;
    a=b=1;
    N=1;

    while (b<X)
         {
             c=a+b;
             a=b;
             b=c;
             ++N;
         }
    printf ("%d\n", N);

    return 0;
}