#include<cstdio>
using namespace std;
int p,i,nr;
void read()
{
	freopen("fact.in","r",stdin);
	freopen("fact.out","w",stdout);
	scanf("%d",&p);
}

int p5(int x)
{
	int cont=0;
	while(x%5==0 && x!=0)
	{
		x/=5;
		cont++;
	}
	return cont;
}

void rez()
{
	if(p==0)
		printf("1\n");
	else
	{
		for(i=5;;i+=5)
		{
			nr+=p5(i);
			if (nr==p)
			{
				printf("%d\n",i);
				break;
			}
			if(nr>p)
			{
				printf("-1\n");
				break;
			}
		}
	}
}

int main()
{
	read();
	rez();
	return 0; 
}