// Program function demonstrates the use of library and
// user-defined functions.

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

float answer(float, float, float);

int main ()
{
    cout.setf(ios::fixed, ios::floatfield);
    cout.setf(ios::showpoint);

    cout  << answer(_____, _____, _____);
    return 0;
}

float answer(float one, float two, float three)
{

    return ((- two + sqrt(pow(two, 2)
	- (_____ * one * three))) / (_____ * one));
}