#include <bits/stdc++.h>

#define forn(i, n) for (int i = 0; i < int(n); i++)

using namespace std;

const int INF = 1e7;

int n;
vector<int> pos;

int main() {
	scanf("%d", &n);
	pos.resize(n);
	forn(i, n)
		scanf("%d", &pos[i]);

	int ans = INF;

	forn(i, n + 1){
		int cur = 0;
		if (i) cur = max(cur, pos[i - 1] - 1);
		if (i != n) cur = max(cur, 1000000 - pos[i]);

		ans = min(ans, cur);
	}

	printf("%d\n", ans);
}