from math import isnan
print('Calculator 1.0')
try:
    firstOperand = input('Enter first number:')
except:
    print('Not a number')

try:
    secondOperand = input('Enter second number')

except:
    print('Not a number')

try:
    operand = input('Enter the operation:')

except:
    print('Not a number')

while True:
    if operand == '+':
        print (float(firstOperand) +float(secondOperand))

    if operand == '-':
        print (float(firstOperand) -float(secondOperand))

    if operand == '*':
        print (float(firstOperand) *float(secondOperand))

    if operand == '%':
        print (float(firstOperand) /float(secondOperand))

else:
    print('Invalid parameters')