#include <cstdio>

unsigned p;

unsigned cinci(int x)
{
	int p=5, ret=0;
	while (p<=x)
	{
		ret+=x/p;
		p*=5;
	}
	return ret;
}

int DeI(int l, int r)
{
	int mij, x;
	if (l<=r)
	{
		mij=(l+r)/2;
		x=cinci(mij);
		if (x==p) return mij/5*5;
		if (x>p) return DeI(l, mij-1);
		else return DeI(mij+1, r);
	}
	return -1;
}

int main()
{
	freopen("fact.in", "r", stdin);
	freopen("fact.out", "w", stdout);
	unsigned n;
	scanf("%u", &p);
	if (!p) printf("1");
	else printf("%d", DeI(1, p*5));
}