# Arup Guha
# 11/8/2025
# SER D1 Problem E: Photo Encoding

n = int(input())

freq = []
for i in range(201):
    freq.append(0)

# Store how many of each number there are.
for i in range(n):
    freq[int(input())] += 1

res = 1
for i in range(201):

    if freq[i] == 0:
        continue

    # If only 1.
    opensq = (i+1) - freq[i]
    cur = (i+1) - opensq//2

    
    res = max(res, cur)

print(res)