Now you see why you should never name a variable after a built-in. ;)
You said yourself that you made a variable named input elsewhere in the code. Judging by your error, you must have done this before those two lines. Also, you must have made this variable hold a string.
By doing this, you overshadowed the built-in input. This means that, when you get to those two lines, input no longer exists as the built-in. Instead, it is a string.
Finally, placing (...) after input throws an error because you can't call a string like a function.
Summed up, you can fix the problem by simply picking a different name for that variable besides input.
inputsomewhere in your code?inputlooks like a likely cause of this issue.