#include <fstream>
#include <cmath>

long n, m;

int suma(int j, int k);
int fact(long p);

int main(int argc, char* argv[])
{
	long p;
	int i;

	ifstream inFILE("fact.in");
	ofstream outFILE("fact.out");

	inFILE >> p;
	outFILE << fact(p);

	return 0;
}

int suma(int j, int k)
{
	long s = 0;

	for (int i = 1; i <= k; i++)
	{
		s = s + floor(j / pow(5,(double)i));
	}

	return s;
}

int fact(long p)
{
	int i;
	long a, b, j;

	if (p == 0)
		return 1;
	else
	{
		m = 1;

		for(i = 1; m <= p;i++)
			m = m + pow(5,(double)i);

		if(p == m-1)
			return -1;
		else 
			m = m - pow(5,(double)--i);

		a = ceil(p * pow(5,(double)i) / m);
		b = floor((p + i) * pow(5,(double)i) / m);

		for(j = a; j < b; j++)
		{
			if (suma(j,i) == p)
				return j;
		}

		return -1;
	
	}

}