Help! My calculator project is stuck at ‘str’ object isn’t callable. Are there anything wrong?

```
def add(x,y):
return x + y
def subtract(x,y) :
return x - y
def multiply(x,y) :
return x * y
def devide(x,y) :
return x / y
print("Enter your choice(from 1 to 4)")
print("1 : add")
print("2 : subtract")
print("3 : multiply")
print("4 : divide")
input = input()
if input == "1":
print("What's your calculation?")
num1 = float(input("First number : "))
num2 = float(input("Second number : "))
print(num1,"+",num2,"=", add(num1,num2))
elif input == "2":
print("What's your calculation?")
num1 = float(input("First number : "))
num2 = float(input("Second number : "))
print(num1,"-",num2,"=", subtract(num1,num2))
elif input == "3":
print("What's your calculation?")
num1 = float(input("First number : "))
num2 = float(input("Second number : "))
print(num1,"*",num2,"=", multiply(num1,num2))
elif input == "4":
print("What's your calculation?")
num1 = float(input("First number : "))
num2 = float(input("Second number : "))
print(num1,"/",num2,"=", devide(num1,num2))
else :
print("Invalid input")
```