lambda_c = float(input('What is λc? '))
Fy = float(input('What is Fy? '))

if lambda_c <= 1.5:
    Fcr = 0.658 ** (lambda_c ** 2) * Fy
else:
    Fcr = 0.877 / (lambda_c ** 2) * Fy

print('The critical buckling stress is:', Fcr)