Buggy python submission (verdict: Time Limit Exceeded):
first_input = list(map(int, input().split()))
number = first_input[0]
steps = first_input[1]

scaffolds = list(map(int, input().split()))

start_cost = scaffolds[0]

costs = []

for i in range(number):
    next_step = i
    next_scaffold = scaffolds[next_step]
    target_cost = -1
    for j in range(steps):
        
        last_step = next_step - (j + 1)
        if -1 < last_step:
            cost = abs(scaffolds[next_step] - scaffolds[last_step]) + costs[last_step]
            if target_cost == -1 or cost < target_cost:
                target_cost = cost

    if 0 < target_cost:
        next_cost = target_cost
    else:
        next_cost = scaffolds[next_step]

    
    costs.append(next_cost)

print(costs[number - 1] - start_cost)

Fixed submission:
first_input = list(map(int, input().split()))
number = first_input[0]
steps = first_input[1]

scaffolds = list(map(int, input().split()))

start_cost = scaffolds[0]

costs = []

for i in range(number):
    next_step = i
    next_scaffold = scaffolds[next_step]
    target_cost = -1
    for j in range(steps):
        
        last_step = next_step - (j + 1)
        if -1 < last_step:
            cost = abs(scaffolds[next_step] - scaffolds[last_step]) + costs[last_step]
            if target_cost == -1 or cost < target_cost:
                target_cost = cost

    if 0 < target_cost:
        next_cost = target_cost
    else:
        next_cost = scaffolds[next_step]

    
    costs.append(next_cost)

print(costs[number - 1] - start_cost)

Buggy python submission (verdict: Time Limit Exceeded):
first_input = list(map(int, input().split()))
number = first_input[0]
steps = first_input[1]

scaffolds = list(map(int, input().split()))

start_cost = scaffolds[0]

costs = [start_cost for i in range(number)]

for i in range(number):
    next_step = i
    next_scaffold = scaffolds[next_step]
    target_cost = -1
    for j in range(steps):
        
        last_step = next_step - (j + 1)
        if -1 < last_step:
            cost = abs(scaffolds[next_step] - scaffolds[last_step]) + costs[last_step]
            if target_cost == -1 or cost < target_cost:
                target_cost = cost

    if 0 < target_cost:
        next_cost = target_cost
    else:
        next_cost = scaffolds[next_step]

    if -1 < next_cost:
        costs[i] = next_cost

print(costs[number - 1] - start_cost)

Fixed submission:
first_input = list(map(int, input().split()))
number = first_input[0]
steps = first_input[1]

scaffolds = list(map(int, input().split()))

start_cost = scaffolds[0]

costs = []

for i in range(number):
    next_step = i
    next_scaffold = scaffolds[next_step]
    target_cost = -1
    for j in range(steps):
        
        last_step = next_step - (j + 1)
        if -1 < last_step:
            cost = abs(scaffolds[next_step] - scaffolds[last_step]) + costs[last_step]
            if target_cost == -1 or cost < target_cost:
                target_cost = cost

    if 0 < target_cost:
        next_cost = target_cost
    else:
        next_cost = scaffolds[next_step]

    
    costs.append(next_cost)

print(costs[number - 1] - start_cost)

Buggy python submission (verdict: Runtime Error):
first_input = list(map(int, input().split()))
number = first_input[0]
steps = first_input[1]

scaffolds = list(map(int, input().split()))

start_cost = scaffolds[0]

costs = [start_cost for i in range(number)]

for i in range(number):
    next_step = i
    next_scaffold = scaffolds[next_step]
    target_cost = -1
    for j in range(steps):
        
        last_step = next_step - (j + 1)
        if -1 < last_step:
            cost = abs(scaffolds[next_step] - scaffolds[last_step]) + costs[last_step]
            if target_cost < cost
            target_cost = cost

    if 0 < len(target_cost):
        next_cost = target_cost
    else:
        next_cost = scaffolds[next_step]

    if -1 < next_cost:
        costs[i] = next_cost

print(costs[number - 1] - start_cost)

Fixed submission:
first_input = list(map(int, input().split()))
number = first_input[0]
steps = first_input[1]

scaffolds = list(map(int, input().split()))

start_cost = scaffolds[0]

costs = []

for i in range(number):
    next_step = i
    next_scaffold = scaffolds[next_step]
    target_cost = -1
    for j in range(steps):
        
        last_step = next_step - (j + 1)
        if -1 < last_step:
            cost = abs(scaffolds[next_step] - scaffolds[last_step]) + costs[last_step]
            if target_cost == -1 or cost < target_cost:
                target_cost = cost

    if 0 < target_cost:
        next_cost = target_cost
    else:
        next_cost = scaffolds[next_step]

    
    costs.append(next_cost)

print(costs[number - 1] - start_cost)

Buggy python submission (verdict: Time Limit Exceeded):
first_input = list(map(int, input().split()))
number = first_input[0]
steps = first_input[1]

scaffolds = list(map(int, input().split()))

start_cost = scaffolds[0]

costs = [start_cost for i in range(number)]

for i in range(number):
    next_step = i
    next_scaffold = scaffolds[next_step]
    last_costs = [-1 for i in range(steps)]
    for j in range(steps):
        
        last_step = next_step - (j + 1)
        if -1 < last_step:
            last_costs[j] = abs(scaffolds[next_step] - scaffolds[last_step]) + costs[last_step]
    target_costs = [k for k in last_costs if 0 <= k]
    if 0 < len(target_costs):
        next_cost = min(target_costs)
    else:
        next_cost = scaffolds[next_step]

    if -1 < next_cost:
        costs[i] = next_cost

print(costs[number - 1] - start_cost)

Fixed submission:
first_input = list(map(int, input().split()))
number = first_input[0]
steps = first_input[1]

scaffolds = list(map(int, input().split()))

start_cost = scaffolds[0]

costs = []

for i in range(number):
    next_step = i
    next_scaffold = scaffolds[next_step]
    target_cost = -1
    for j in range(steps):
        
        last_step = next_step - (j + 1)
        if -1 < last_step:
            cost = abs(scaffolds[next_step] - scaffolds[last_step]) + costs[last_step]
            if target_cost == -1 or cost < target_cost:
                target_cost = cost

    if 0 < target_cost:
        next_cost = target_cost
    else:
        next_cost = scaffolds[next_step]

    
    costs.append(next_cost)

print(costs[number - 1] - start_cost)