#include<cstdio>

int p;

int zero(int n)
{
	int rez=0;
	while(n)
	{
		n/=5;
		rez+=n;
	}
	return rez;
}

int calcul()
{
	if(p==0)
		return 1;
	int z,st=5,dr=1<<30,m;
	while(st!=dr)
	{
		m=(st+dr)>>1;
		z=zero(m);
		if(p<=z)
			dr=m;
		else
			st=m+1;
	}
	z=zero(st);
	if(z==p)
		return st;
	return -1;
}

int main()
{
	freopen("fact.in","r",stdin);
	freopen("fact.out","w",stdout);
	scanf("%d",&p);
	printf("%d\n",calcul());
	return 0;
}