#include <cstdio>
int main()
{
	freopen ("fact.in","r",stdin);
	freopen ("fact.out","w",stdout);
	
	int p,x=0,i=1,aux=25;
	scanf ("%d",&p);
	x=p*5;
	for (int j=25;j<=100;j+=25)
		if (x>j)
			x-=5;
	for (int j=125;j<=x;j+=25)
	{
		if (aux<j)
		{
			aux*=5;
			i++;
		}
		if (aux==j)
			x=x-(i*5);
		else
			x-=5;
	}
		
	
	
	
	if (p==0)
		printf ("1 \n");
	else
		printf ("%d \n",x);
}