#include <bits/stdc++.h>   using namespace std;   int main() {     ios_base::sync_with_stdio(0);     cin.tie(0);     cout.tie(0);     long long int n;     cin >> n;     long long int arr[n];     for (int i = 0; i < n; i++) cin >> arr[i];     long long int pre = 0;     int counter = 0;     while (counter < n && arr[counter] != 0) {       pre++;       counter++;     }     long long int post = 0;     counter = n - 1;     while (counter >= 0 && arr[counter] != 0) {       counter--;       post++;     }     counter = 0;     long long int mx = 0;     for (int i = 0; i < n; i++) {       if (arr[i] == 0) {         if (mx < counter) mx = counter;         counter = 0;       } else {         counter++;       }     }     if (counter > mx) mx = counter;     if (mx < pre + post) mx = pre + post;     cout << mx <<   n ;     return 0;   }   