0, 1, 1, 2, 3, 5, 8, 13, .....

0 
1 
1 
2 -- fback2
3 -- fback1
5

read in a number  4
0
1
1
2
3

print each Fibonacci number less than that

======================
read in an integer upto





fback2 <- 0
fback1 <- 1

while fib < upto:
	fib = fback1 + fback2
	if fib < upto
		print fib
	fback2 <- fback1
	fback1 <- fib

while forever:
	fib = fback1 + fback2
	if fib < upto
		print fib
	else
		drop out of loop
	fback2 <- fback1
	fback1 <- fib

=================

upto = int(input("Number> "))

fback2 = 0
fback1 = 1

while True:
	fib = fback1 + fback2
	if fib < upto:
		print(fib)
	else
		break
	fback2 = fback1
	fback1 = fib






upto = 4
-------------
fback2 <- 0
fback1 <- 1
fib <- 0 + 1 = 1
--------------
fback2 <- 1
fback1 <- 1
fib <- 1 + 1 = 2
--------------
fback2 <- 1
fback1 <- 2
fib <- 1 + 2 = 3
--------------
fback2 <- 2
fback3 <- 3
fib <- 2 + 3 = 5