#include <fstream>
#include <iostream>
using namespace std;
int main()
{
	long long p;
	ifstream f("fact.in");
	ofstream g("fact.out");
	f>>p;
	
	if(p == 0)
	{
		g<<1;
		return 0;
	}
	
	long long k = 0,i;
	for(i = 5; k < p; i+=5)
	{
		int c = i;
		while(c % 5 == 0)
		{
			++k;
			c/=5;
		}
	}
	
	if(k == p)
	{
		g<<i-5;
		return 0;
	}
	else g<<-1;
	return 0;
}