int m = Integer.parseInt(br.readLine()); int[] num = new int[m + 1]; String[] s = br.readLine().split(" "); for(int j = 0; j < m; j ++) { num[j] = Integer.parseInt(s[j]); } num[m] = 0; int[] arr = new int[m + 1]; int count = 0; int index = -1; if (num[0] == 0) { index = 0; } int max = 0; for(int j = 0; j <= m; j ++) { if (num[j] == 1) { count ++; } else { arr[j] += count; max = Math.max(max, arr[j]); if (index >= 0) { arr[index] += count; max = Math.max(max, arr[index]); } count = 0; index = j; } } System.out.println(max == m ? m - 1 : max);