#include<stdio.h>

int tuzi(int n);

int main(){
	int n;
	scanf("%d", &n);
	int month = tuzi(n);
	printf("%d", month);
	return 0;
}

int tuzi(int n){
	int startcouple = 0;
	int endcouple = 0;
	int children1 = 1;
	int month = 1;
	while(endcouple + children1 < n){
		month ++;
		endcouple += children1;
		children1 = startcouple;
		startcouple = endcouple;
	}
	return month;
}