#include <stdio.h>
	
int main(void) 
{
	int x, N = 0;
	scanf("%d", &x);
	int first = 0, second = 1;	
	while (second < x) {
		int swp = second;
		second = second + first;
		first  = swp;
		N++;
	}
	printf("%d", N);
	
	return 0;
}