#include <bits/stdc++.h>

using namespace std;

template<typename T1, typename T2>
ostream& operator<<(ostream& out, const pair<T1, T2>& x) {
    return out << x.first << ' ' << x.second;
}

template<typename T1, typename T2>
istream& operator>>(istream& in, pair<T1, T2>& x) {
    return in >> x.first >> x.second;
}

template<typename T>
istream& operator>>(istream& in, vector<T>& a) {
    for(auto& x: a) {
        in >> x;
    }
    return in;
};

template<typename T>
ostream& operator<<(ostream& out, const vector<T>& a) {
    for(auto x: a) {
        out << x << ' ';
    }
    return out;
};

double AB, AC, AD, BC, BD, CD;

void read() { cin >> AB >> AC >> AD >> BC >> BD >> CD; }

double gaussian_det(vector<vector<double>> mat) {
    int n = mat.size();
    double det = 1.0;
    for(int i = 0; i < n; ++i) {
        int pivot = i;
        for(int j = i + 1; j < n; ++j) {
            if(abs(mat[j][i]) > abs(mat[pivot][i])) {
                pivot = j;
            }
        }
        if(pivot != i) {
            swap(mat[i], mat[pivot]);
            det = -det;
        }
        if(abs(mat[i][i]) < 1e-10) {
            return 0.0;
        }
        det *= mat[i][i];
        for(int j = i + 1; j < n; ++j) {
            double factor = mat[j][i] / mat[i][i];
            for(int k = i; k < n; ++k) {
                mat[j][k] -= factor * mat[i][k];
            }
        }
    }
    return det;
}

void solve() {
    // We know that the volume of the pyramid is 1/3 * h * B, where B is the
    // area of the base and h is the height. The area of the base can easily be
    // calculated with Heron's formula, while the height we can bash / compute
    // using complex numbers or by defining a vector base and solving a system.
    // This approach is a bit tedious so we might want to consider alternatives.
    //
    // There is also an alternative approach using more theory. We can use
    // Cayley-Menger's determinant, which can be thought of as a generalization
    // of Heron's formula. It essentially gives us a formula for the volume of
    // the n-dimensional simplex, given by the pairwise distances between all
    // points. In particular, the formula says that the determinant of the
    // pairwise distance matrix with 1s added as the final row and column, times
    // (-1)^(n+1)/((n!)^2*2^n) is the square of the volume of the n-dimensinoal
    // simplex. This is precisely what we have here for n=4 and so we implement
    // this. More details can be found here:
    //
    //     https://en.wikipedia.org/wiki/Cayley%E2%80%93Menger_determinant

    double a2 = AB * AB, b2 = AC * AC, c2 = AD * AD;
    double d2 = BC * BC, e2 = BD * BD, f2 = CD * CD;
    vector<vector<double>> m(5, vector<double>(5));
    m[0] = {0, 1, 1, 1, 1};
    m[1] = {1, 0, a2, b2, c2};
    m[2] = {1, a2, 0, d2, e2};
    m[3] = {1, b2, d2, 0, f2};
    m[4] = {1, c2, e2, f2, 0};
    double determinant = gaussian_det(m);
    double volume = sqrt(abs(determinant) / 288.0);
    cout << fixed << setprecision(4) << volume << endl;
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    int T = 1;
    // cin >> T;
    for(int test = 1; test <= T; test++) {
        read();
        // cout << "Case #" << test << ": ";
        solve();
    }

    return 0;
}
