#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; }