枚举

/*****************************************
Note  :
******************************************/
#include <queue>
#include <math.h>
#include <stack>
#include <stdio.h>
#include <iostream>
#include <vector>
#include <iomanip>
#include <string.h>
#include <algorithm>
#define LL long long
#define IL inline
const int N = 1e6+10;
const int INF = 0x3f3f3f3f;
using namespace std;
IL int read()
{
    char ch = getchar();
    int f = 1, num = 0;
    while(ch>'9'||ch<'0')
    {
        if(ch=='-') f = -1;
        ch=getchar();
    }
    while(ch>='0'&&ch<='9')
        num = num*10+ch-'0', ch = getchar();
    return num*f;
}
int n,ans;
int main()
{
	cin>>n;
	for(int i = 1,x;i<=n;i++)
    {
        cin>>x;
        ans=max(ans,min(x-1,1000000-x));
    }
    printf("%d\n",ans);
}