# include <stdio.h>
long long pas=1<<30;
int p;
int zero(int n)

{
	int nr=0;
	while(n)
	{
		nr+=n/5;
		n/=5;
	}
	return nr;
}
int caut ()
{
	int i;
	for(i=1;pas;pas>>=1)
		if(zero(i+pas)<p)
			i+=pas;
	if(zero(i+1) != p)
		return -1;
	else
		return i+1;
}
int main()
{
	
	freopen("fact.in","r",stdin);
	freopen("fact.out","w",stdout);
	scanf("%d",&p);
	if(p==0) printf("1");
		else 
	printf("%d",caut());
	return 0;
}