calculator

import math
def add( a,b ):
    return a + b
def sub( a, b ):
    return a - b
def mul( a, b ):
    return a * b
def div( a, b ):
    return a / b
def mod ( a, b):
    return a % b
def cinterest ( p, r, n, t ):
    return p * m.pow((1 + r/n), n * t)
def sinterest ( p, t, r ):
    return ( p * t * r )/100

print("select operation. ")
print(" 1.Add")
print(" 2.Subtract")
print(" 3.Multiply")
print(" 4.Divide")
print(" 5.cinterest")
print(" 6.sinterest")
while True :
    choice = input("Enter choice(1/2/3/4/5/6): ")
    if choice in ('1', '2', '3',  '4', ):
        num1 = float(input("Enter first number: "))
        num2 = float(input("Enter second number: "))
        if choice == '1':
             res = num1 + num2
             print("Result = ", res)
        elif choice == '2':
               res = num1 - num2
               print("Result = ", res)
        elif choice == '3':
               res = num1 * num2
               print("Result = ", res)
        elif choice == '4':
               res = num1 / num2
               print("Result", res)
    elif choice in ('5', '6',):
        p = float(input("Enter principal: "))
        t = float(input("Enter the time in years: "))
        r = float(input("Enter the rate of interest: "))
        if choice == '1':
              res = num1 + num2
              print("Result = ", res)
        elif choice == '2':
              res = num1 - num2
              print("Result = ", res)
        elif choice == '3':
              res = num1 * num2
              print("Result = ", res)
        elif choice == '4':
              res = num1 / num2
              print("Result", res)
        elif choice == '5':
              res = p * (math.pow((1 + r / 100), t))
              print("Result = ", res)
        elif choice == '6':
              res = p * t * r
              print("Result", res)
        break
    else:
        print("Invalid Input")