#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
ll cp(ll n)
{
    ll k=sqrt(n);
    return k*k==n;
}
int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0); cout.tie(0);
 ll n,a[100000],tong=0,dem=0;
 cin>>n;
 for(ll i=0;i<n;++i)
 {
     cin>>a[i];
     if(cp(a[i]))
     {
         dem++;
         tong+=a[i];
     }
 }
if(dem==0) {cout<<"-";}
else {cout<<fixed<<setprecision(1)<<(float)tong/dem;}
 
}