01: #include <iostream>
02: #include <cmath>
03: using namespace std;
04:
05:int main()
06:{  double area;
07:    cout << "Please enter the area of a square: ";
08:    cin >> area;
09:
10:    if (area >= 0)
11:       cout << "The side length is " << sqrt(area) << "\n";
12:    else
13:       cout <<"Error: Negative area.\n";
14:
15:    return 0;
16: }