using namespace std;
#include<fstream>
ifstream fin("fact.in");
ofstream fout("fact.out");
int zero (int a)
{
	int s=0,p=5;
	while(a>=p)
	{
		s=s+a/p;
		p=p*5;
	}
	return s;
}
int main()
{
	int N,p=5,a;
	fin>>N;
	if(N==0)
		fout<<"1";
	else
	{
		while((p-1)/4<=N)
			p=p*5;
		p=(p/5-1)/4;
		a=zero(p);
		while(N>a)
		{
			p++;
			a=zero(p);
		}
		if(N<a)
			fout<<"-1";
		else
			fout<<p;
	}
	return 0;
}