#include <fstream.h>
long int n,i,j,nr,p;
ifstream f("fact.in");
ofstream g("fact.out");
int main()
{
	f>>n;
	f.close();
	nr=0;i=0;
	while(n>nr)
	{
		i=i+5;
		p=i;
		while(p%5==0)
		{
			nr++;
			p=p/5;
		}
	}
	g<<i;
	g.close();
	return 0;
}