#pragma GCC optimize("O3")
#include <bits/stdc++.h>
#define ll long long
#define rep(i,n) for(ll i=0;i<(n);i++)
#define pll pair<ll,ll>
#define pii pair<int,int>
#define pq priority_queue
#define pb push_back
#define eb emplace_back
#define fi first
#define se second
#define endl '\n'
#define ios ios_base::sync_with_stdio(0),cin.tie(0),cout.tie(0);
#define lb(c,x) distance(c.begin(),lower_bound(all(c),x))
#define ub(c,x) distance(c.begin(),upper_bound(all(c),x))

using namespace std;


int main(){
    ll n;
    cin >> n;
    vector<ll> a(n);
    rep(i,n){
        cin >> a[i];
        a[i]%=10;
    }
    vector<vector<ll>> dp(n+1,vector<ll>(10,-1));
    dp[0][0]=0;
    rep(i,n){
        rep(j,10){
            dp[i+1][j]=max(dp[i+1][j],dp[i][j]);
            if(dp[i][(j-a[i]+10)%10]!=-1){
                dp[i+1][j]=max(dp[i][(j+10-a[i])%10]+1,dp[i+1][j]);
            }
        }
    }
    cout << dp[n][0] << endl;
    return 0;
}