The quadratic equation ax2+bx+c=0 plays an important role in mathematics. It has a well-known solution:
Write a Python function main() to compute the two roots. You should input a,b and c from keyboard, and then print the two roots. Assume the discriminant D= b2-4ac is positive. That is, you do not need to check the sign of discriminant and your input should satisfy b2-4ac>0.