#Bisection method
emin = -2.3
emax = -2.4
while True:
    average = (emin + emax)/2
    #print("test")
    if (emin-emax) < 0.00000001:
        print(average)
        break
    guess = emin
    for i in range(len(episilon)):
        if i > 1:
            phi[i] = (2+h**2 * f(episilon[i-1]))*phi[i-1]-phi[i-2]
        #plt.plot(episilon,phi)
    eminphi = phi[950]
    #print(eminphi)
    guess = emax
    for i in range(len(episilon)):
        if i > 1:
            phi[i] = (2+h**2 * f(episilon[i-1]))*phi[i-1]-phi[i-2]
        #plt.plot(episilon,phi)
    emaxphi = phi[950]
    #print(emaxphi)
    guess = average
    for i in range(len(episilon)):
        if i > 1:
            phi[i] = (2+h**2 * f(episilon[i-1]))*phi[i-1]-phi[i-2]
    averagephi = phi[950]
    if np.sign(averagephi) == np.sign(eminphi):
        emin = average
    if np.sign(averagephi) == np.sign(emaxphi):
        emax = average