package main

import (
	"bufio"
	"fmt"
	"os"
)

func main() {
	reader := bufio.NewReader(os.Stdin)
	var n int
	fmt.Fscan(reader, &n)

	maxTime := 0
	for i := 0; i < n; i++ {
		var a int
		fmt.Fscan(reader, &a)
		time1 := a - 1
		time2 := 1000000 - a
		minTime := time1
		if time2 < minTime {
			minTime = time2
		}
		if minTime > maxTime {
			maxTime = minTime
		}
	}
	fmt.Println(maxTime)
}