MY code is wronganswer .why? Can you help me?I'm grateful for you help

#include<iostream>
#include<cmath>
#include<stack>
#include<iomanip>
#include<cstdio>
using namespace std;
typedef unsigned long long ull;

stack<double> st;
int main()
{
    ull a;
    cin>>a;
    while(!cin.eof())
    {
      st.push(sqrt((double)a));
      cin>>a;
    }

    cout<<setprecision(4)<<fixed;
    while(!st.empty())
    {
       cout<<st.top()<<endl;
       st.pop();
    }
//  system("pause");
}