Looking for critique on my code

[zeevo234]

So I've been working on a relatively short script for solving a math problem, and it works, but there's a specific part that I want to optimize with a procedure. However, I can't figure out how to implement one. 

print("Enter the corresponding values of the standard quadratic function: y=ax^2+bx+c")
a = input("Enter the A value:")
    if a == "stop" or a == "Stop" or a == "STOP":
        print("\nStopping program...")
        sys.exit()
b = input("Enter the B value:")
    if b == "stop" or b == "Stop" or b == "STOP":
        print("\nStopping program...")
        sys.exit()
c = input("Enter the C value:")
    if c == "stop" or c == "Stop" or c == "STOP":
        print("\nStopping program...")
        sys.exit()