#include<iostream> #include<cstring> #include<cstdio> #include<cmath> using namespace std; double f[20]; int n; double deal(double mid) { double sum=0; for(int i=0;i<=n;i++) sum+=f[i]*pow(mid,n-i); return sum; } int main() { while(scanf("%d",&n)>0&&n) { for(int i=0;i<=n;i++) scanf("%lf",&f[i]); double left=-1,right=1,mid; while(right-left>1e-6) { mid=(left+right)/2; if(deal(mid)>=0) left=mid; else right=mid; } printf("%.2lf ",left-1.0); } return 0; }