#include <cstdio>
unsigned long N;

unsigned long nrzerouri(unsigned long x)
{
	unsigned long c=5,rez=0;
	while(c<=x)
	{
		rez+=x/c;
		c*=5;
	}
	
	return rez;
}

unsigned long cautbin()
{
	unsigned long p=1<<31,a=0;
	while(p)
	{
		if(nrzerouri(a+p)<N)
			a+=p;
		p>>=1;
	}
	
	if(nrzerouri(a+1)==N)
		return a+1+1;
	else
		return 0;
}

int main()
{
	freopen("fact.in","r",stdin);
	freopen("fact.out","w",stdout);
	scanf("%u",&N);
	printf("%d",cautbin()-1);
	
	return 0;	
}