#include <stdio.h>
int main()
{
	long p,val=0,a,b,c,c1,d;
	freopen("factorial.in","r",stdin);
	freopen("factorial.out","w",stdout);
	scanf("%d",&p);
	a=0; b=1000;
	while ((a!=b)&&(val!=p))
	{
		c=(a+b)/2; d=c;
		if (c%10>5)
			c=c/10*10+5;
		if (c%10<5)
			c=c/10*10;
		val=0;
		while (c>0)
		{
			c1=c;
			while (c1%5==0)
			{
				c1=c1/5;
				val++;
			}
			c=c-5;
		}
		if (val<p)
			a=d;
		if (val>p)
			b=d;
	}
	printf("%d",d-1);
}