N = int(input())
a = list(map(int, input().split()))
for i in range(N):
    a[i] = a[i] % 10
dp = [[0] * 10 for _ in range(N + 1)]
dp[0][0] = 1
for i in range(N):
    for j in range(10):
        if dp[i][j] != 0:
            dp[i + 1][(j + a[i]) % 10] = max(dp[i + 1][(j + a[i]) % 10], dp[i][j] + 1)
        dp[i + 1][j] = max(dp[i][j], dp[i + 1][j])

print(dp[N][0] - 1)