#include<fstream>
using namespace std;

ifstream in("fact.in");
ofstream out("fact.out");
int fact(int p)
{
	if(p==0)
		return 1;
	else if(p==1)
		return 5;
	else if(p==2)
		return 10;
	else
	{
		int t=2;
		int i=15;
		while(t<p)
		{
			int j=i;
			while(j%5==0)
			{j=j/5;++t;};
			++i;
		}
		if(p==t)
			return i-1;
		else
			return -1;
	}
}
int main()
{
	int p;
	in>>p;
	out<<fact(p);

	return 0;
}