nums = input()
m = input()

mugs = []

for i in m:
    mugs.append(i)

brands = {}
odd_counter = 0

for i in mugs:
    try:
        brands[i] += 1
    except:
        brands[i] = 1

for i in brands:
    if brands[i] % 2 != 0:
        odd_counter += 1

while odd_counter > 1:
    odd_counter = 0
    curr_remove = mugs.pop(len(mugs) - 1)
    brands[curr_remove] -= 1
    for i in brands:
        if brands[i] % 2 != 0:
            odd_counter += 1

print(len(mugs))