#include<fstream>
using namespace std;
int main()
{
	ifstream f("fact.in");
	ofstream g("fact.out");
	int v[100000001];
	long long p,inc,sf,i,j;
	f>>p;
	if(p==0)
		g<<1;
	else
	{
		v[1]=1;
		for(i=2;i<=p;i++)
		{
			v[i]=v[i-1]+1;
			j=i;
			while(j%5==0)
			{
				j=j/5;
				v[i]++;
			}
		}
		inc=1;
		sf=p;
		while(inc!=(sf-1))
		{
		if(v[(inc+sf)/2]>p)
			sf=(inc+sf)/2;
		else inc=(inc+sf)/2;
		}
		if(v[inc]==p)
			g<<5*inc;
		if(v[sf]==p)
			g<<5*sf;
		if((v[inc]!=p)&&(v[sf]!=sf))
			g<<-1;
	}
	}