TypeError: Can't convert 'int' object to str implicitly

I am trying to write a text game and I have run into an error in the function I am defining that lets you basically spend your skill points after you make your character. At first, the error stated that I was attempting to subtract a string from an integer in this part of the code:balance - strength. Obviously that was wrong so I fixed it with strength = int(strength)... but now I am getting this error which I have never seen before(new programmer) and I am stumped on what exactly it is trying to tell me and how I fix it.

Here is my code for the part of the function that isn't working:

def attributeSelection():
    balance = 25
    print("Your SP balance is currently 25.")
    strength = input("How much SP do you want to put into strength?")
    strength = int(strength)
    balanceAfterStrength = balance - strength
    if balanceAfterStrength == 0:
        print("Your SP balance is now 0.")
        attributeConfirmation()
    elif strength < 0:
        print("That is an invalid input. Restarting attribute selection. Keep an eye on your balance this time!")
        attributeSelection()
    elif strength > balance:
        print("That is an invalid input. Restarting attribute selection. Keep an eye on your balance this time!")
        attributeSelection()
    elif balanceAfterStrength > 0 and balanceAfterStrength < 26:
        print("Ok. You're balance is now at " + balanceAfterStrength + " skill points.")
    else:
        print("That is an invalid input. Restarting attribute selection.")
        attributeSelection()

And here is the error I get when I get to this part of the code in the shell:

    Your SP balance is currently 25.
How much SP do you want to put into strength?5
Traceback (most recent call last):
  File "C:\Python32\APOCALYPSE GAME LIBRARY\apocalypseGame.py", line 205, in <module>
    gender()
  File "C:\Python32\APOCALYPSE GAME LIBRARY\apocalypseGam