Flipping The Pairs

The program asks for a number and then prints out all the positive integer values from 1 up to the number. However, the order of the numbers is changed so that each pair or numbers is flipped. That is, 2 comes before 1, 4 before 3 and so forth. For example:

Please type in a number: 6214365

num = int(input("Please type in a number: "))r = 2t = 1while True:    if t >= num:        break    print(r)    print(t)    r += 2    t += 2

The code works fine with even numbers but then struggles with odd numbers. For example with the input 5 the result should be:

Please type in a number: 521435

But instead my output comes out as:

Please type in a number: 52143

Any help would be appreciated.