/*
\u3000\u3000\u3000\u3000\u3000\u3000\u3000\u3000\u3000\u3000\u3000 \u2227\uff3f\u2227
\u3000\u3000\u3000\u3000\u3000 \u2227\uff3f\u2227 \u3000\uff08\u00b4<_\uff40 \uff09\u3000 Welcome to My Coding Space ^_^
\u3000\u3000\u3000\u3000 \uff08 \u00b4_\u309d`\uff09\u3000/\u3000 \u2312i
\u3000\u3000\u3000\u3000\uff0f\u3000\u3000\u3000\uff3c\u3000 \u3000  |\u3000|
\u3000\u3000\u3000 /\u3000\u3000 /\uffe3\uffe3\uffe3\uffe3/\u3000|\u3000|
\u3000 \uff3f_(__\uff86\u3064/\u3000\u3000 \u3000 / .| .|\uff3f\uff3f\uff3f\uff3f
\u3000 \u3000\u3000\u3000\uff3c/\uff3f\uff3f\uff3f\uff3f/\u3000\uff08u\u3000\u2283
*/

package main

import (
  "fmt"
)

const Hat_N = 4e5 + 3

func main() {
  var n, cnt, tar int;
  var v [Hat_N]int
  cnt, tar = 0, 0
  fmt.Scan(&n);
  for i := 1; i <= n; i++ {
    fmt.Scan(&v[i])
    v[n + i] = v[i]
  }
  for i := 1; i <= (n << 1); i++ {
    if (v[i] != 0) {
      cnt++
    } else {
      if (cnt > tar) {
        tar = cnt;
      }
      cnt = 0
    }
  }
  fmt.Println(tar)
}

/*#################################################################
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#################################################################*/