#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define io ios::sync_with_stdio(0), cin.tie(0);
#define endl '\n'
#define MXN (ll)1e6+5
int main(){
    int n;
    cin >> n;
    int arr[n-1];
    int nw = 0, mx = 0;
    for(int i=0;i<n-1;i++) {
        cin >> arr[i];
        if(arr[i] == 0) {
            nw++;
        } else {
            nw = 0;
        }
        mx = max(nw, mx);
    }
    if(mx == n-1){
        cout << mx << endl;
    } else
        cout << mx+1 << endl;
}