n = int(input()) a = list(map(int, input().split())) max_val = 0 for i in range(n): val = 0 if i - 2 >= 0 and abs(a[i - 2] - a[i]) <= 2: val += 1 if i - 1 >= 0 and abs(a[i - 1] - a[i]) <= 2: val += 1 if i + 1 < n and abs(a[i + 1] - a[i]) <= 2: val += 1 if i + 2 < n and abs(a[i + 2] - a[i]) <= 2: val += 1 max_val = max(max_val, val) print(max_val)