F2C / C2F converter

I still need to make a UI, so below the code in front (it works very well on my laptop)

# mathematical-formula F to C: C = (F - 32) x .5556
# mathematical-formula C to F: F = C * 1.8 + 32

# To do: layout... GUI?

def F2C():
    run = 0
    while run < 1:
        Fahrenheit = input ("\r\nHow many degrees Fahrenheit (No decimals)?\r\n('q' to quit, start with '-' for negative value): ")
        if Fahrenheit.isnumeric() == False:
            if Fahrenheit == "q":
                from sys import exit
                exit()
            elif Fahrenheit.startswith("-"):
                Celcius = (int(Fahrenheit) - 32) * 0.5556
                print("\nCelcius: " + str(Celcius))
            else:
                print("\nOnly numeric values")
        else:
            Celcius = (int(Fahrenheit) - 32) * 0.5556
            print("\nCelcius: " + str(Celcius))

def C2F():
    run = 0
    while run < 1:
        Celcius = input ("\r\nHow many degrees Celcius (No decimals)?\r\n('q' to quit, start with '-' for negative value): ")
        if Celcius.isnumeric() == False:
            if Celcius == "q":
                from sys import exit
                exit()
            elif Celcius.startswith("-"):
                Fahrenheit = (int(Celcius) * 1.8) + 32
                print("\nFahrenheit: " + str(Fahrenheit))
            else:
                print("\nOnly numeric values")
        else:
            Fahrenheit = (int(Celcius) * 1.8) + 32
            print("\nFahrenheit: " + str(Fahrenheit))

choice_run = 0
while choice_run < 1:
    choice = input("Convert Celcius to Fahrenheit (c)\r\nor Fahrenheit to Celcius (f)\r\n?: ")
    if choice == "c":
        C2F()
    elif choice == "f":
        F2C()
    else:
        print("\nOnly c or f\n")