y[0] = b[0] / L[0][0];
    for (int i = 1; i<n; i++) {
        int sum = 0;
        for (int j = 0; j<i; j++)
            sum += L[i][j] * y[j];
        y[i] = (b[i] - sum) / L[i][i];
    }

    x[n - 1] = y[n - 1];
    for (int i = n - 2; i >= 0; i--) {
        int sum = 0;
        for (int j = n - 1; j >= i + 1; j--)
            sum += x[j] * U[i][j];
        x[i] = y[i] - sum;
    }