#include <iostream>
#include <cmath>
using namespace std;
int main() {
float a, b, c, r;
cin >> a >> b >> c;
if (a + b >= c && a + c >= b && b + c >= a) {
r = (sqrt(((a + b + c) / 2) * (((a + b + c) / 2) - a) * (((a + b + c) / 2) - b) * (((a + b + c) / 2) - c)) / ((a + b + c) / 2)) * 100;
if (int(r) % 10 == 0)
if (int(r) / 10 % 10 == 0)
cout << int(r) / 100 << ".00";
else
cout << int(r) / 100 << '.' << int(r) / 10 % 10 << 0;
else
cout << int(r) / 100 << '.' << int(r) / 10 % 10 << int(r) % 10;
} else
cout << "Imposibil";
return 0;
}