#include <cstdio>

int zero(int n) // calculeaza nrul de zerouri din desc lui n!
{
	int r=0;
	while (n)
	{
		r=r+n/5;
		n=n/5;
	}
	return r;
}

int caut(int p)
{
	int i,pas=(1<<30);
	for (i=0;pas;pas>>=1)
		if (zero(i+pas)<=p-1)
			i+=pas;
	if (zero(i+1)!=p) 
		return -1;
	return i+1;
}
int main()
{
	int n;
	freopen("fact.in","r",stdin);
	freopen("fact.out","w",stdout);
	scanf("%d",&n);
	printf("%d",caut(n));
	return 0;
}