what is wrong???

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

int main ()
{
    int a, b, c, d;
    cin >> a >> b >> c >> d;
    if (a*b == c*d)
    {
        cout << "Impossible.";
        return 0;
    }

    double s;
    s = (c*d*a*a + c*d*b*b - a*b*c*c - a*b*d*d)/(c*d-a*b);
    if (s < 0)
    {
        cout << "Impossible.";
        return 0;
    }

    int ans;
    s = (sqrt(s) * 1000);
    if (s - (int)s < 0.5)
        ans = (int)s;
    else
        ans = (int)s + 1;
    cout << "Distance is " << ans << " km.";
    return 0;
}

Edited by author 26.02.2012 18:37