Write a function int interval_unfold_count(int n); that returns the length of the shortest sequence of operations resulting in either L or R being equal to N.

Two integer variables L and R are initially equal to 0 and 1 respectively (i.e. L = 0 and R = 1).
The values of these variables can be manipulated using the following operations: operation 'L' is the assignment L = 2*L-R, operation 'R' is the assignment R = 2*R-L.
Given an integer N we want to find what is the shortest sequence of such operations necessary to make either L or R equal to N. For example, given N = 21, the following sequence of operations:
(initially L = 0, R = 1),
L = 2*L-R (makes L = -1, R = 1),
L = 2*L-R (makes L = -3, R = 1),
R = 2*R-L (makes L = -3, R = 5),
L = 2*L-R (makes L = -11, R = 5),
R = 2*R-L (makes L = -11, R = 21)
makes one of the variables (namely R) equal to N (i.e. after the last operation N = R = 21). This sequence consists of 5 operations and there is no shorter sequence that would make either L or R equal 21.
Write a function int interval_unfold_count(int n);
that returns the length of the shortest sequence of operations resulting in either L or R being equal to N. For example, given N = 21 the function should return 5.