#include<iostream>
#include<cmath>
#include<iomanip>
using namespace std;

int main() {
    long long a[100000] = {0};
    int i = 0;
    while (cin >> a[i]) {
        i++;
    }
    for (int j = i-1; j >= 0; j--) {
        cout << fixed << setprecision(4) << sqrt(a[j]) << endl;
    }
}

How did you think "100,000" is enough for the input?

You shouldn't allocate big arrays on stack. You should allocate big array in heap or use vector.