D

import kotlin.math.abs

private data class Rectangle(val x1: Int, val y1: Int, val x2: Int, val y2: Int) {
    companion object {
        @JvmStatic
        internal inline val input
            get() = readLine()!!
                .trim()
                .split(' ')
                .map(String::toInt)
                .let { (x1, y1, x2, y2) -> Rectangle(x1, y1, x2, y2) }

        @JvmStatic
        internal fun getCommonArea(vararg rectangles: Rectangle): Long {
            for (i in 0 until rectangles.size - 1)
                for (q in i + 1 until rectangles.size)
                    if (!(rectangles[i] isHaveCommonAreaWith rectangles[q]))
                        return 0

            val xs = rectangles.flatMap { (x1, _, x2) -> listOf(x1, x2) }.sorted()
            val ys = rectangles.flatMap { (_, y1, _, y2) -> listOf(y1, y2) }.sorted()
            return (xs[rectangles.size] - xs[rectangles.size - 1]).toLong() *
                    (ys[rectangles.size] - ys[rectangles.size - 1]).toLong()
        }
    }

    inline val area
        get() = abs(x1 - x2 + 0L) * abs(y1 - y2 + 0L)

    infix fun isHaveCommonAreaWith(other: Rectangle): Boolean {
        val (x1F, x2F) = listOf(x1, x2).sorted()
        val (x1S, x2S) = listOf(other.x1, other.x2).sorted()
        if (x2F < x1S || x2S < x1F) return false

        val (y1F, y2F) = listOf(y1, y2).sorted()
        val (y1S, y2S) = listOf(other.y1, other.y2).sorted()
        if (y2F < y1S || y2S < y1F) return false

        return true
    }

    infix fun `&`(other: Rectangle): Long = getCommonArea(this, other)
}

fun main() {
    val first = Rectangle.input
    val second = Rectangle.input
    val third = Rectangle.input

    val fs = first `&` second
    val ft = first `&` third
    val st = second `&` third

    print(first.area + second.area + third.area - fs - ft - st + Rectangle.getCommonArea(first, second, third))
}