#include <bits/stdc++.h>
using namespace std;

#define ull unsigned long long
#define endl '\n'
#define ll long long
const int N = 2e6 + 5;
bool v[N];
int sum[N];
int main(){
        ios_base::sync_with_stdio(false);
        cin.tie(0);
        cout.tie(0);
        //freopen("test.txt", "r", stdin);
        int n, k = 0;
        cin >> n;
        for (int i = 1; i <= n; i++){
                int a;
                cin >> a;
                if (a != 0) v[a + 1000000] = 1;
                else k++;
        }
        int cnt = 0;
        int ans = 0;
        sum[0] = -1000000;
        for (int i = -1000000; i <= 1000000; i++){
                if (v[i + 1000000] == 0) {
                        cnt++;
                        sum[cnt] = i;
                }
                ans = max(ans, i - sum[max(cnt - k, 0)]);
        }
        cout << ans;
}