#include<fstream>
using namespace std;
int main()
{
	ifstream fcin("fact.in");
	ofstream fcout("fact.out");
	long long p,n,i,j,m,x,nr;
	bool ok=1;
	fcin>>p;
	if(p==0)
		fcout<<1;
	else
	{
		for(i=1,j=5*p;i<=j && ok==1;)
		{
			m=(i+j)/2;
			x=m;
			nr=0;
			while(x!=0)
			{
				nr+=x/5;
				x/=5;
			}
			if(nr==p)
			{
				fcout<<m-m%5;
				ok=0;
			}
			else
				if(nr<p)
					i=m+1;
				else
					j=m-1;
		}
		if(ok==1)
			fcout<<-1;
	}
	return 0;
}