N = int(input())
A = list(map(int, input().split()))

dp = [[-1]*10 for _ in range(N+1)]
dp[0][0] = 0
for i in range(N):
    m = A[i] % 10       
    for j in range(10):
        if dp[i][j] == -1:
            continue
        dp[i+1][j] = max(dp[i+1][j], dp[i][j])
        x = (m+j)%10
        dp[i+1][x] = max(dp[i+1][x], dp[i][j] + 1)
print(dp[N][0])