How to fix TypeError: unsupported operand type(s) for -: 'str' and 'str'?

Question

Python

Hello. I am new and just learning python. I tried to make a calculator and got such an error when trying to count on -
Maybe someone knows how to solve this?
Here is the code:
what = input ("Select an action (+ or -):")

a = input("Enter the first number: ")
b = input("Enter the second number: ")

if what == "+":
c = a + b
print("Result: " + c)

elif what == "-":
c = a - b
print("Result: " + c)

else:
print("Invalid operation!")

Answer 1

c = int(a) + int(b)
c = int(a) - int(b)