#include<stdio.h>
#include<math>
using namespace std;
int main(){
	int P,N,
	freopen("factorial.in","r",stdin);
	freopen("factorial.out","w",stdout);
	scanf("%d",P);
	Pi=P;
	N=P*5;
	for(i=2;pow(5,i)<N;i++){
		if (Pi==pow(5,i-1)+x)
			
		P-=(i-1);
		N=P*5;