Go: package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
)

var sc = bufio.NewScanner(os.Stdin)

func nextInt() int {
	sc.Scan()
	n, _ := strconv.Atoi(sc.Text())
	return n
}

func main() {
	sc.Split(bufio.ScanWords)
	N := nextInt()
	max, cnt := 0, 0
	for i := 0; i < N; i++ {
		cnt++
		if nextInt() == 0 {
			cnt = 0
		}
		if cnt > max {
			max = cnt
		}
	}
	fmt.Println(max + 1)
}

C++: #include<stdio.h>
#include <algorithm>
#include <cassert>
#include <cctype>
#include <climits>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <iostream>
#include <iterator>
#include <list>
#include <map>     
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <iomanip>
#include <stack>
#include <string>
#include <vector>
using namespace std;
#define ll long long
#define ld long double
#define roop(a,t) for(int a=0;a<t;a++) 
int main()
{
	cin.tie(0);
	ios::sync_with_stdio(false);
int n;
cin>>n;
int u[100];
int ans=0;
int conti=0;
for(int i=0;i<n;i++){
cin>>u[i];
if(u[i]==1){conti++;}
else{ans=max(ans,conti);conti=0;}
}cout<<ans<<endl;

	return 0;
}

C++: #include <iostream>
using namespace std;
#include <vector>
#include <sstream>


int main(void){
    // 自分の得意な言語で
    // Let's チャレンジ！！

    string str;
    int N;
    int count = 0;
    int ConsectiveOnes = 0;
    int Max_Ones = 0;
    int ThisNum;
    while(getline(cin, str)){
        stringstream ss;
        ss << str;
        if(count == 0){
            ss >> N;
        }
        else{
            for(int i = 0;i < N;i++){
                ss >> ThisNum;
                if(ThisNum){
                    ConsecutiveOnes++;
                }
                else{
                    ConsecutiveOnes = 0;
                }
                if(ConsecutiveOnes > Max_Ones){
                    Max_Ones = ConsecutiveOnes;
                }
            }
        }
        
        
        count++;
    }
    
    
    
    cout << Max_Ones + 1 << endl;
    return 0;
}

C++: //2017
#include<iostream>
using namespace std;
int main(void){
	int i,n,a[100],cnt=0;
	cin>>n;
	for(i=0;i<n;i++){
		cin>>a[i];
	}
	for(i=0;i<n;i++){
		if(a[i]==1){
			if(a[i+1]==1){
				cnt+=2;
				i=i+2;
			}
			else{
				cnt++;
			}
		}
		else if(a[i]==0){
			cnt=0;
		}
	}
	cout<<cnt+2<<endl;
	
	return 0;
}

C++: #include<iostream>
using namespace std;

int main(){
    int n;
    cin >> n;
    int A[n];
    int count=0,max=0;
    for(int i=0;i<n;i++){
        cin>>A[i];
        if(A[i]==1){
            count+=1;
            continue;
            }
        else{
            if(max<count){
                max=count;
            }
            count=0;
        }
    }
    if(max<count){
        max=count;
    }
    cout<<max+1<<endl;
    return 0;
}

C++: /////////////////////////////////////////////////////////
//
//  c/temp.cpp file
//  Last Updated: 2018-10-23 ...Maybe
//
//    I hope you adding this code to the setting file
//    alias g++='g++ -std=c++1y -DDEBUG_LOCAL'
//
/////////////////////////////////////////////////////////

#include <bits/stdc++.h>

using namespace std;

#define fi first
#define se second
#define mp make_pair
#define pb push_back

//#define int long long

#define _overload3(_1,_2,_3,name,...) name
#define _REP(i,n) REAP(i,0,n)
#define REAP(i,a,b) for(int i=int(a);i<int(b);++i)
#define REP(...) _overload3(__VA_ARGS__,REAP,_REP,)(__VA_ARGS__)

#define _REPR(i,n) REAPR(i,n,0)
#define REAPR(i,a,b) for(int i=int(a-1);i>=int(b);--i)
#define REPR(...) _overload3(__VA_ARGS__,REAPR,_REPR,)(__VA_ARGS__)

#define ALL(a) a.begin(),a.end()
#define rALL(a) a.rbegin(),a.rend()

#define coutALL(a) {int loop_coutALL=0;for(auto e:a) cout<<(loop_coutALL++?" ":"")<<e; cout<<endl;}

#define coutYN(a) cout<<((a)?"YES":"NO")<<endl;
#define coutYn(a) cout<<((a)?"Yes":"No")<<endl;
#define coutyn(a) cout<<((a)?"yes":"no")<<endl;

#define pcnt __builtin_popcount
#define buli(x) __builtin_popcountll(x)

const int INF=1145141919;
//const long long INF=114514191911451419;
const int MOD=(int)1e9+7;
const double EPS=1e-12;
const int dx[]={1,0,-1,0},dy[]={0,1,0,-1};
//const int dx[]={-1,-1,-1,0,1,1,1,0},dy[]={-1,0,1,1,1,0,-1,-1};

using vi=vector<int>;
using vvi=vector<vi>;
using vs=vector<string>;

typedef pair<int,int> pii;
typedef pair<int,string> pis;
typedef pair<string,int> psi;
typedef pair<string,string> pss;

typedef long long ll;

template<typename T> istream &operator >> (istream &is, vector<T> &v){for(T &x:v) is>>x;return is;}
template<typename T> ostream &operator << (ostream &os, vector<T> &v){int i=0;for(T &x:v) os<<(i++?" ":"")<<x;return os;}

ll rev(ll n){ll x=0;for(;n>0;){x=x*10+n%10;n/=10;}return x;}

ll upper(ll n,ll m){return (n+m-1)/m;};
ll rounding(ll n){return (long double)n+0.5;};

bool inG(ll x,ll n){return 0<=x && 0<n;}
bool outG(ll x,ll n){return x<0 || n<=x;}

inline int qp(int a,ll b){if(!b)return 1;int ans=1;do{if(b&1)ans=1ll*ans*a;a=1ll*a*a;}while(b>>=1);return ans;}
inline int qp(int a,ll b,int mo){if(!b)return 1;int ans=1;do{if(b&1)ans=1ll*ans*a%mo;a=1ll*a*a%mo;}while(b>>=1);return ans;}

inline ll fac(ll k,ll n){ll a=1;for(int i=0;i<n;i++)a*=k--;return a;}
inline ll fac(ll k,ll n,int mo){ll a=1;for(int i=0;i<n;i++)a*=k--,a%=mo;return a;}

inline int dsum(ll n){int a=0;for(;n;n/=10)a+=n%10;return a;}

struct Arithmetic{Arithmetic(){cin.tie(0);ios::sync_with_stdio(0);cout<<fixed<<setprecision(20);}};

//#define DEBUG_LOCAL

#ifdef DEBUG_LOCAL
template<typename T> void deb(T a){cerr<<"deb: "<<a<<"です"<<endl;}
#define debl {cerr<<"debug: "<<__LINE__<<"行目だ"<<endl;}
void what_cr(){cout<<__GCC_ATOMIC_CHAR16_T_LOCK_FREE<<" ←？"<<endl;}
//ori_func S

//ori_func E
#else
template<typename T>void deb(T a){}
#define debl
void what_cr(){}void t_t(){}
#endif

signed main(){

  Arithmetic Exception;

  int n;
  cin>>n;

  vi a(n);
  cin>>a;

  int ans=0,check=0;
  REP(i,n){

    if(a[i]) check++;
    else check=0;

    ans=max(ans,check);

  }

  cout<<ans+1<<endl;

  return 0;

}