import sys
def I(): return int(sys.stdin.readline().rstrip())
def LI2(): return list(map(int,sys.stdin.readline().rstrip()))  #空白なし


N = I()
S = LI2()
c1,c3,c5,c7,c9 = 0,0,0,0,0
for s in S:
    if s == 1:
        c1 += 1
    elif s == 3:
        c3 += 1
    elif s == 5:
        c5 += 1
    elif s == 7:
        c7 += 1
    else:
        c9 += 1

ans = c1//2+c3+c5+c7

if c1 % 2 == 1 and c9 >= 1:
    index = 0
    for i in range(N):
        if S[i] == 1:
            index = i
            break
    for i in range(index,N):
        if S[i] == 9:
            ans += 1
            break

print(ans)