#include<fstream.h>

long h(long m);


int main()
{
	ifstream fin("fact.in");
	ofstream fout("fact.out");

	long p;

	fin>>p;

	fin.close();

	fout<<h(p);
	fout.close();
	return 0;
}

long h(long m)
{
	if (m==0)
	return 1;
	long R=0,x=0,i=0,g,k=0;
	while (R<m)
	{

		i=i+5;
		g=i;
		while (g%5==0)
		{
			g=g/5;
			x++;
		}
		R=x;
	}
	return i;
}