#include<cstdio>

using namespace std;

int p,n,i,j,step;

int v(int a)
{
	int k=0;
	while(a) k+=a/5,a/=5;
}

int main()
{
	freopen("factorial.in","r",stdin);
	freopen("factorial.out","w",stdout);
	
	scanf("%d",&p);
	
	n=p*40;
	
	for(step=1;step<=p;step<<=1);
	
	for(i=0;step;step>>=1)
		if(i+step<=n&&v(i+step)>p) 
			i+=step;
			
	while(i%5) --i;
	
	if(v(i)==p) printf("%d\n",i);
	else printf("-1\n");
	
	fclose(stdin);
	fclose(stdout);
	
	return 0;

}