#include<cstdio>

#include<algorithm>

#include<cmath>

using namespace std;

typedef long long LL;

LL a[];

LL b[];

int n;

bool isok(LL x) {

    for (int i=;i<=n;i++) b[i]=a[i];

    for (int i=;i<=n;i++) {

        LL t1=b[i-];

        LL t2=t1*x;

        b[i]-=t2;

    }

    if (b[n]==) return ;

    else         return ;

}

int main ()

{

    while (scanf("%d",&n)!=EOF) {

            a[]=;

            for (int i=;i<=n;i++) {

                scanf ("%lld",&a[i]);

            }

            LL sum=;

            LL p=abs(a[n]);

            for (LL i=;i*i<=p;i++) {

                if (p%i==) {

                    if (isok(i)) sum-=i;

                    if (isok(-i)) sum+=i;

                    if (i==a[n]/i) continue;

                    if (isok(a[n]/i)) sum-=a[n]/i;

                    if (isok(-a[n]/i)) sum+=a[n]/i;

                }

            }

            printf("%.2lf\n",sum*1.00);

    }

    return ;

}