#include<iostream>
#include<math.h>
#include<iomanip>


using namespace std;
int main()
{
    double num[4];
    int a;
    for(int a(0);a<4;a++)
    cin >> num[a];
    system("cls");
    for(int a(0);a<4;a++)
    cout << num[a] << ' ';
    for(int a(3);a>=0;a--)
    {cout << "\n" << fixed << setprecision(4) << sqrt(num[a]) << endl;}
    cout << "\n";

    return 0;
}

Who told you that there is exactly 4 numbers in the input? For example, your code will give wrong answer on the following test:
1 2 3 4 5

Also, I'm not sure if system calls are allowed on timus.