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

print(dp[-1][0])