#include <cstdio>
#include <iostream>
using namespace std;
unsigned long long N,P,copie,i,cifra;
unsigned long long contor;
int main()
{

	FILE *intrare,*iesire;
	intrare=fopen("fact.in","r");
	iesire=fopen("fact.out","w");
	fscanf(intrare,"%lld",&P);
	fclose(intrare);
	N=1;
	i=1;
	if(P==0) fprintf(iesire,"%d",1);
	else
	{
		while(contor!=P)
		{
			contor=0;
			N=N*i;
			copie=N;
			while(copie!=0)
			{
				cifra=copie%10;
				if(cifra==0) contor=contor+1;
				else break;
				copie=copie/10;
			}
			i=i+1;
			
		}
		fprintf(iesire,"%lld",i-1);
	}
	cout <<contor;
	return 0;
}