qq

import math

def f(a):
    best_modify_steps = {-1: 1, 0: 0, 1: 1}
    for i in range(1, len(a)):
        prev_best_modify_steps = best_modify_steps.copy()
        diff = a[i] - a[i - 1]
        for current_modify in [-1, 0, 1]:
            best_modify_steps[current_modify] = min(
                [
                    prev_best_modify_steps[prev_modify]
                    + (0 if current_modify == 0 else 1)
                    if (diff + current_modify - prev_modify) >= 0
                    else math.inf
                    for prev_modify in [-1, 0, 1]
                ]
            )
    return min(best_modify_steps.values())

a = [3, 5, 3, 4, 8, 6]
print(f(a))
# [3, 5-1, 3+1, 4, 8-1, 6+1] => 4