def shift(arr)
    arr[0] = arr[1]
    arr[1] = arr[2]
    arr[2] = arr[3]
    arr[3] = []
end

def push(arr, val)
    shift(arr)

    if arr[1]
        arr[1] << val
    end

    if arr[2]
        arr[2] << val
    end

    arr[3] << val
end

def run(f)
    increments = 0
    buffer = []

    f.each do |line|
        measurement = Integer(line)

        push(buffer, measurement)

        if buffer[0] and buffer[1] and buffer[0].length() == 3 and buffer[1].length() == 3 and buffer[1].sum() > buffer[0].sum()
            increments += 1
        end
    end

    return increments
end